Light emitting diode with high efficiency

ABSTRACT

A light emitting diode includes: a substrate; a semiconductor stack disposed on the substrate and including a lower semiconductor layer, an upper semiconductor layer and an active layer interposed between the lower semiconductor layer and the upper semiconductor layer, the semiconductor stack having an isolation groove exposing the substrate through the upper semiconductor layer, the active layer and the lower semiconductor layer; a first electrode pad and an upper extension portion electrically connected to the upper semiconductor layer; a second electrode pad and a lower extension portion electrically connected to the lower semiconductor layer; a connecting portion connecting the upper extension portion and the lower extension portion to each other across the isolation groove; a first current blocking layer interposed between the lower extension portion and the lower semiconductor layer; and a second current blocking layer interposed between the second electrode pad and the lower semiconductor layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.15/490,492, filed on Apr. 18, 2017, and claims priority from and thebenefit of Korean Patent Application No. 10-2016-0047054, filed on Apr.18, 2016, Korean Patent Application No. 10-2016-0149627, filed on Nov.10, 2016, and Korean Patent Application No. 10-2017-0020233, filed onFeb. 14, 2017, all of which are incorporated by reference for allpurposes as if fully set forth herein.

BACKGROUND Field

Exemplary embodiments of the present disclosure relate to a lightemitting diode, and more particularly, to a light emitting diode withhigh luminous efficacy.

Discussion of the Background

A light emitting diode (LED) refers to a solid state light emittingdevice that converts electrical energy into light. Light emitting diodesare broadly used as light sources for backlight units, lightingapparatus, traffic signals, large displays, and the like. Withincreasing demand for LEDs for lighting and expansion of applicationrange to high current density and high output fields, there is a needfor improvement in characteristics of LEDs for stable operation uponhigh current driving.

Generally, the intensity of light output from a light emitting diodeincreases with increasing current density applied to a light emittingdiode. However, an increase in current density causes a decrease inexternal quantum efficiency, that is, a droop phenomenon. The droopphenomenon increases light loss with increasing current density andobstructs improvement in luminous efficacy as measured in lm/W.

SUMMARY

Exemplary embodiments of the present disclosure provide a light emittingdiode suitable for a light emitting device with high luminous efficacy.

Exemplary embodiments of the present disclosure provide a light emittingdiode that suppresses a droop phenomenon.

Exemplary embodiments of the present disclosure provide a light emittingdiode that prevents disconnection of a connecting portion whichelectrically connects at least two light emitting cells to each other.

In accordance with one exemplary embodiment of the present disclosure, alight emitting diode includes: a substrate; first to fourth lightemitting cells disposed on the substrate; a first electrode pad; and asecond electrode pad, wherein each of the light emitting cells includesa lower semiconductor layer, an upper semiconductor layer, and an activelayer interposed between the lower semiconductor layer and the uppersemiconductor layer; the lower semiconductor layer includes a firstlower semiconductor layer and a second lower semiconductor layerseparated from each other; the first light emitting cell and the secondlight emitting cell share the first lower semiconductor layer; the thirdlight emitting cell and the fourth light emitting cell share the secondlower semiconductor layer; the first light emitting cell is connected inseries to the third light emitting cell; the second light emitting cellis connected in series to the fourth light emitting cell; the firstelectrode pad is electrically connected to the upper semiconductorlayers of the first light emitting cell and the second light emittingcell; and the second electrode pad is electrically connected to thelower semiconductor layers of the third light emitting cell and thefourth light emitting cell.

In accordance with another exemplary embodiment of the presentdisclosure, a light emitting diode includes: a substrate; asemiconductor stack disposed on the substrate and including a lowersemiconductor layer, an upper semiconductor layer and an active layerinterposed between the lower semiconductor layer and the uppersemiconductor layer, the semiconductor stack having an isolation grooveexposing the substrate through the upper semiconductor layer, the activelayer and the lower semiconductor layer; a first electrode pad and anupper extension portion electrically connected to the uppersemiconductor layer; a second electrode pad and a lower extensionportion electrically connected to the lower semiconductor layer; aconnecting portion connecting the upper extension portion and the lowerextension portion to each other across the isolation groove and having agreater width than the upper extension portion and the lower extensionportion; a first current blocking layer interposed between the lowerextension portion and the lower semiconductor layer; and a secondcurrent blocking layer interposed between the second electrode pad andthe lower semiconductor layer, wherein the first current blocking layerincludes a plurality of dots separated from one another, a width each ofthe dots is greater than the width of the lower extension portion, thesecond current blocking layer has a smaller width than the secondelectrode pad, and the shortest distance from the isolation groove tothe first current blocking layer is greater than a separation distancebetween the dots.

According to exemplary embodiments, the light emitting diode includes aplurality of light emitting cells arranged on a substrate such that thelight emitting cells are connected to each other in series or inparallel. With the structure wherein the light emitting cells areconnected to each other in series, the light emitting diode can bedriven with low current, thereby improving luminous efficacy throughreduction in current density. In addition, with the structure whereinthe light emitting cells are connected to each other in parallel, thelight emitting diode allow electric current input to the light emittingcells to be uniformly spread to the light emitting cells, therebysuppressing the droop phenomenon. Further, the light emitting diodeincludes the current blocking layer interposed between the lowersemiconductor layer and the lower extension portion and having a greaterwidth than the lower extension portion to prevent current crowding in aparticular region while allowing the current to spread over a wideregion of the light emitting cell, thereby further suppressing the droopphenomenon.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosed technology, and are incorporated in andconstitute a part of this specification, illustrate exemplaryembodiments of the disclosed technology, and together with thedescription serve to describe the principles of the disclosedtechnology.

FIG. 1 is a plan view of a light emitting diode according to oneexemplary embodiment of the present disclosure,

FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1,

FIG. 3 is a cross-sectional view taken along line B-B of FIG. 1, and

FIG. 4 is a cross-sectional view taken along line C-C of FIG. 1.

FIG. 5 is an enlarged plan view of a first electrode pad of FIG. 1 and

FIG. 6 is a cross-sectional view taken along line D-D of FIG. 5.

FIG. 7 is an enlarged plan view of a second electrode pad of FIG. 1 and

FIG. 8 is a cross-sectional view taken along line E-E of FIG. 7.

FIG. 9 is a plan view of a light emitting diode according to anotherexemplary embodiment of the present disclosure,

FIG. 10 is a cross-sectional view taken along line F-F of FIG. 9,

FIG. 11 is a cross-sectional view taken along line G-G of FIG. 9, and

FIG. 12 is a cross-sectional view taken along line H-H of FIG. 9.

FIG. 13A is an enlarged plan view of one exemplary embodiment of aconnecting portion of FIG. 9 and

FIG. 13B is a cross-sectional view taken along line I-I of FIG. 13A.

FIG. 14A is an enlarged plan view of another exemplary embodiment of theconnecting portion of FIG. 9 and

FIG. 14B is a cross-sectional view taken along line I′-I′ of FIG. 14A.

FIG. 15, FIG. 16, and FIG. 17 are plan views of light emitting diodesaccording to other exemplary embodiments of the present disclosure.

FIG. 18A, FIG. 18B, and FIG. 18C are sectional views of the lightemitting diodes according to the exemplary embodiments of the presentdisclosure, showing side surfaces thereof.

FIG. 19 is a top view of light emitting diodes according to exemplaryembodiments of the present disclosure, showing a package mountingstructure.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, exemplary embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings. Thefollowing embodiments are provided by way of example so as to fullyconvey the spirit of the present disclosure to those skilled in the artto which the present disclosure pertains. Accordingly, the presentdisclosure is not limited to the embodiments disclosed herein and canalso be implemented in different forms. In the drawings, widths,lengths, thicknesses, and the like of elements can be exaggerated forclarity and descriptive purposes. It will be understood that, when anelement such as a layer, film, region or substrate is referred to asbeing “on” another element, it can be directly on the other element orintervening elements may also be present. In contrast, when an elementis referred to as being “directly on” another element, there are nointervening elements present. Throughout the specification, likereference numerals denote like elements having the same or similarfunctions. Also, the singular forms “a”, “an”, and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising”, “includes” and/or “including”, “have” and/or“having” when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

In accordance with one exemplary embodiment of the present disclosure, alight emitting diode includes: a substrate; first to fourth lightemitting cells disposed on the substrate; a first electrode pad; and asecond electrode pad. In this exemplary embodiment, each of the lightemitting cells includes a lower semiconductor layer, an uppersemiconductor layer, and an active layer interposed between the lowersemiconductor layer and the upper semiconductor layer, wherein the lowersemiconductor layer includes a first lower semiconductor layer and asecond lower semiconductor layer separated from each other; the firstlight emitting cell and the second light emitting cell share the firstlower semiconductor layer; the third light emitting cell and the fourthlight emitting cell share the second lower semiconductor layer; thefirst light emitting cell is connected in series to the third lightemitting cell; the second light emitting cell is connected in series tothe fourth light emitting cell; the first electrode pad is electricallyconnected to the upper semiconductor layer of each of the first lightemitting cell and the second light emitting cell; and the secondelectrode pad is electrically connected to the lower semiconductorlayers of the third light emitting cell and the fourth light emittingcell. Accordingly, the light emitting diodes include the light emittingcells connected to each other in series-parallel connection, and thuscan reduce current density for driving and can achieve uniform currentspreading to the light emitting cells, thereby improving luminousefficacy.

In addition, since the first and second light emitting cells share thefirst lower semiconductor layer and the third and fourth light emittingcells share the second lower semiconductor layer, the light emittingdiode according to this exemplary embodiment allow a simplemanufacturing process and can minimize reduction in luminous area due toisolation between light emitting cells.

Specifically, the first lower semiconductor layer and the second lowersemiconductor layer may be isolated from each other by an isolationgroove exposing an upper surface of the substrate, and the first lightemitting cell and the third light emitting cell may be isolated from thesecond light emitting cell and the fourth light emitting cell by a mesaisolation grove exposing the first lower semiconductor layer and thesecond lower semiconductor layer, respectively.

In some exemplary embodiments, the light emitting diode may furtherinclude a transparent electrode layer disposed on the uppersemiconductor layer of each of the light emitting cells.

The first electrode pad may be disposed on the mesa isolation groove andmay straddle the first light emitting cell and the second light emittingcell. Here, the transparent electrode layer may be disposed between eachof the first and second light emitting cells and the first electrodepad.

The light emitting diode may further include a current blocking layerdisposed under the first electrode pad. The current blocking layer mayhave a larger area than the first electrode pad such that the firstelectrode pad is placed only in an upper region of the current blockinglayer, and a portion of the current blocking layer may be disposedbetween each of the first and second light emitting cells and thetransparent electrode layer.

The transparent electrode layer on each of the first and second lightemitting cells may include an opening exposing the current blockinglayer, and the first electrode pad may be connected to the currentblocking layer through the opening.

The light emitting diode may further include upper extension portionsdisposed on the transparent electrode layer of each of the lightemitting cells and electrically connected to the transparent electrodelayer; and current blocking layers disposed between the transparentelectrode layers and the light emitting cells under the upper extensionportions. A width of each of the current blocking layers may be lessthan three times the width of each of the upper extension portions. Thecurrent blocking layers aid in uniform current spreading over a lightemitting cell region. In addition, light loss by the current blockinglayers can be reduced by adjusting the width of the current blockinglayer.

The light emitting diode may further include a lower extension portionconnected to the lower semiconductor layer of each of the light emittingcells. The lower extension portions may include linear regions extendingin the same direction, the linear region of the lower extension portionof the first light emitting cell may be parallel to the linear region ofthe lower extension portion of the third light emitting cell, and thelinear region of the lower extension portion of the second lightemitting cell may be parallel to the linear region of the lowerextension portion of the fourth light emitting cell.

The upper extension portions disposed on the transparent electrodelayers of the first light emitting cell and the second light emittingcell are electrically connected to the first electrode pad, and thelower extension portions connected to the lower semiconductor layers ofthe third light emitting cell and the fourth light emitting cell areelectrically connected to the second electrode pad. Thus, the lightemitting cells are connected in series-parallel between the firstelectrode pad and the second electrode pad.

Each of the upper extension portions may include a primary upperextension portion configured to surround a portion of the correspondinglower extension portion and a secondary upper extension portionprotruding from the primary upper extension portion.

The secondary upper extension portion on each of the first lightemitting cell and the second light emitting cell may be disposed toconnect the primary upper extension portion to the first electrode pad,and the secondary upper extension portions on the third light emittingcell and the fourth light emitting cell may be disposed to connect theprimary upper extension portions on the third light emitting cell andthe fourth light emitting cell to the lower extension portions of thefirst light emitting cell and the second light emitting cell,respectively.

The secondary upper extension portions on the first light emitting celland the second light emitting cell may be connected to the primary upperextension portions closer to the mesa isolation groove than thecorresponding lower extension portions. Thus, the lengths of thesecondary upper extension portions can be reduced.

The light emitting diode may further include connecting portions whichconnect the lower extension portions on the first and second lightemitting cells to the secondary upper extension portions on the thirdand fourth light emitting cells, respectively. The light emitting diodemay further include an insulating layer insulating the connectingportions from the second lower semiconductor layers of the third lightemitting cell and the fourth light emitting cell.

The lower extension portions of the third light emitting cell and thefourth light emitting cell may further include lower extension portionsin a curved region connecting the lower extension portions in the linearregion to the second electrode pad. Furthermore, the second electrodepad may be disposed on the second lower semiconductor layer exposed bythe mesa isolation groove.

The light emitting diode may further include an insulating layercovering side surfaces of the upper semiconductor layer and the activelayer around the second electrode pad. The insulating layer can preventshort circuit by a bonding material in a ball-bonding process.

The insulating layer covering the side surfaces of the uppersemiconductor layer and the active layer may be separated from thetransparent electrode layer.

In some exemplary embodiments, the first electrode pad and the secondelectrode pad may be disposed to face each other, wherein the firstelectrode pad may be disposed near one edge of the substrate and thesecond electrode pad may be disposed near the other edge of thesubstrate facing the one edge thereof.

Each of the primary upper extension portions on the third light emittingcell and the fourth light emitting cell may include an inner enddisposed between the lower extension portion of the third light emittingcell and the lower extension portion of the fourth light emitting cell,and an outer end disposed outside the lower extension portion, and theouter end of the lower extension portion may be disposed closer to theother edge of the substrate than the inner end.

The light emitting diode may have a symmetrical structure with respectto an imaginary line passing through the first electrode pad and thesecond electrode pad.

In accordance with another exemplary embodiment of the presentdisclosure, a light emitting diode includes: a substrate; asemiconductor stack disposed on the substrate and including a lowersemiconductor layer, an upper semiconductor layer and an active layerinterposed between the lower semiconductor layer and the uppersemiconductor layer, the semiconductor stack having an isolation grooveexposing the substrate through the upper semiconductor layer, the activelayer and the lower semiconductor layer; a first electrode pad and anupper extension portion electrically connected to the uppersemiconductor layer; a second electrode pad and a lower extensionportion electrically connected to the lower semiconductor layer; aconnecting portion connecting the upper extension portion and the lowerextension portion to each other across the isolation groove and having agreater width than the upper extension portion and the lower extensionportion; a first current blocking layer interposed between the lowerextension portion and the lower semiconductor layer; and a secondcurrent blocking layer interposed between the second electrode pad andthe lower semiconductor layer, wherein the first current blocking layerincludes a plurality of dots separated from one another, a width each ofthe dots is greater than the width of the lower extension portion, thesecond current blocking layer has a smaller width than the secondelectrode pad, and the shortest distance from the isolation groove tothe first current blocking layer is greater than a separation distancebetween the dots.

A connection region in which the connecting portion and the lowerextension portion are connected to the lower semiconductor layer betweenthe isolation groove and the current blocking layer may have a greaterlength than a connection region in which the lower extension portion isconnected to the lower semiconductor layer between two adjacent dots.

The upper extension portion may be separated from the lower extensionportion and a distal end of the lower extension portion may be directlyconnected to the lower semiconductor layer. The upper extension portionmay be disposed to surround the distal end of the lower extensionportion.

In this structure, a diagonal distance from the distal end of the lowerextension portion to the upper extension portion may be greater than ahorizontal distance from the distal end of the lower extension portionto the upper extension portion. Here, the horizontal distance means adistance from the distal end of the lower extension portion to the upperextension portion in a horizontal direction that is parallel to thesubstrate, and the diagonal distance means a distance from the distalend of the lower extension portion to the upper extension portion in aslanted direction with respect to the horizontal direction.

The first current blocking layer and the second current blocking layermay include an SiO₂ layer or a distributed Bragg reflector layer.

The light emitting diode may further include a transparent electrodelayer disposed on the upper semiconductor layer, wherein a part of thetransparent electrode layer may be disposed between the uppersemiconductor layer and the first electrode pad and between the uppersemiconductor layer and the upper extension portion.

The light emitting diode may further include a third current blockinglayer disposed between the upper semiconductor layer and the transparentelectrode layer under the first electrode pad.

The transparent electrode layer may have an opening exposing the thirdcurrent blocking layer and the first electrode pad may be connected tothe third current blocking layer through the opening. The third currentblocking layer may have a larger area than the first electrode pad suchthat the first electrode pad is disposed only on the third currentblocking layer.

The semiconductor stack may include a plurality of light emitting cellsdefined by the isolation groove or the mesa isolation groove and each ofthe plurality of light emitting cells may include the lower extensionportion and the upper extension portion.

The connecting portion may be disposed on the isolation groove andelectrically connect the upper extension portion and the lower extensionportion of two adjacent light emitting cells.

The plurality of light emitting cells may include first to fourth lightemitting cells; the lower semiconductor layer may include a first lowersemiconductor layer and a second lower semiconductor layer separatedfrom each other by the isolation groove; the first light emitting celland the second light emitting cell may share the first lowersemiconductor layer; the third light emitting cell and the fourth lightemitting cell may share the second lower semiconductor layer; the firstlight emitting cell may be connected in series to the third lightemitting cell through the connecting portion; and the second lightemitting cell may be connected in series to the fourth light emittingcell through the connecting portion.

The lower extension portions of the light emitting cells may includelinear regions extending in the same direction; the linear region of thelower extension portion of the first light emitting cell may be coaxialwith the linear region of the lower extension portion of the third lightemitting cell; and the linear region of the lower extension portion ofthe second light emitting cell may be coaxial with the linear region ofthe lower extension portion of the fourth light emitting cell.

The first electrode pad may be disposed on the mesa isolation groove soas to straddle the first light emitting cell and the second lightemitting cell, and the second electrode pad may be disposed on the mesaisolation groove so as to be electrically connected to the second lowersemiconductor layer.

The upper extension portion disposed on the transparent electrode layerof each of the first light emitting cell and the second light emittingcell may be electrically connected to the first electrode pad, and thelower extension portion disposed on the lower semiconductor layer ofeach of the third light emitting cell and the fourth light emitting cellmay be electrically connected to the second electrode pad.

The upper extension portion of each of the light emitting cells mayinclude a primary upper extension portion configured to surround aportion of the corresponding lower extension portion and a secondaryupper extension portion protruding from the primary upper extensionportion.

The secondary upper extension portion on each of the first lightemitting cell and the second light emitting cell may be disposed toconnect the primary upper extension portion to the first electrode pad,and the secondary upper extension portions on the third light emittingcell and the fourth light emitting cell may be disposed to connect theprimary upper extension portions on the third light emitting cell andthe fourth light emitting cell to the lower extension portions of thefirst light emitting cell and the second light emitting cell,respectively.

The first light emitting cell and the third light emitting cell may beconnected in parallel to the second light emitting cell and the fourthlight emitting cell through the first electrode pad and the secondelectrode pad.

Each of the light emitting cells may include a step on a side surface ofthe substrate, and the side surface of the substrate may be exposed.

Hereinafter, exemplary embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is a plan view of a light emitting diode according to oneexemplary embodiment of the present disclosure, FIG. 2 is across-sectional view taken along line A-A of FIG. 1, FIG. 3 is across-sectional view taken along line B-B of FIG. 1, and FIG. 4 is across-sectional view taken along line C-C of FIG. 1. FIG. 5 is anenlarged plan view of a first electrode pad of FIG. 1 and FIG. 6 is across-sectional view taken along line D-D of FIG. 5. FIG. 7 is anenlarged plan view of second electrode pads of FIG. 1 and FIG. 8 is across-sectional view taken along line E-E of FIG. 7.

Referring to FIG. 1, the light emitting diode according to thisexemplary embodiment includes a first light emitting cell C1, a secondlight emitting cell C2, a third light emitting cell D1, and a fourthlight emitting cell D2 disposed on a substrate 21. In addition, thelight emitting diode includes a first electrode pad 37, a secondelectrode pad 35, upper extension portions 37 a, 37 b, 37 c, 37 d, lowerextension portions 35 a, 35 b, connecting portions 35 c, currentblocking layers 31 a, 31 d, insulating layers 32 a, 32 b, and atransparent electrode layer 33. As best shown in FIG. 2 to FIG. 4, eachof the light emitting cells C1, C2, D1, D2 includes a lowersemiconductor layer 23 a or 23 b, an active layer 25, and an uppersemiconductor layer 27.

The substrate 21 may be selected from any substrates suitable for growthof a gallium nitride-based semiconductor layer. For example, thesubstrate 21 may include a sapphire substrate, a silicon carbidesubstrate, a gallium nitride substrate, an aluminum nitride substrate, asilicon substrate, and the like. In this exemplary embodiment, thesubstrate 21 may be a patterned sapphire substrate (PSS).

The lower semiconductor layers 23 a, 23 b, the active layer 25 and theupper semiconductor layer 27 may be Group III-V based, particularly,gallium nitride-based compound semiconductor layers. These semiconductorlayers may include, for example, a nitride semiconductor, such as (Al,Ga, In)N. The lower semiconductor layers 23 a, 23 b may include n-typedopants (for example, Si) and the upper semiconductor layer 27 mayinclude p-type dopants (for example, Mg), or vice versa. The activelayer 25 may have a multi-quantum well (MQW) structure and thecomposition of the active layer 25 may be adjusted to emit light in adesired wavelength range. The first to fourth light emitting cells C1,C2, D1, D2 may be formed by sequentially growing the lower semiconductorlayers 23 a, 23 b, the active layer 25 and the upper semiconductor layer27 on the substrate 21, followed by patterning these semiconductorlayers. These semiconductor layers may be grown by, for example, metalorganic vapor deposition, molecular beam epitaxy, hydride vapor phaseepitaxy, and the like.

The first light emitting cell C1 and the second light emitting cell C2are isolated from the third light emitting cell D1 and the fourth lightemitting cell D2 by an isolation groove 30 a, respectively, and thefirst light emitting cell C1 and the third light emitting cell D1 areisolated from the second light emitting cell C2 and the fourth lightemitting cell D2 by a mesa isolation groove 27 a, respectively. That is,the first and second light emitting cells C1, C2 are isolated from thethird and fourth light emitting cells D1, D2, respectively, by anisolation process, in which the isolation groove 30 a is formed toexpose the substrate 21. Meanwhile, the first light emitting cell C1 andthe third light emitting cell D1 are isolated from the second lightemitting cell C2 and the fourth light emitting cell D2, respectively, bya mesa etching process, in which the mesa isolation groove 27 a isformed to expose the lower semiconductor layers 23 a, 23 b. In thisstructure, the first light emitting cell C1 and the second lightemitting cell C2 share a first lower semiconductor layer 23 a, and thethird light emitting cell D1 and the fourth light emitting cell D2 sharea second lower semiconductor layer 23 b. Further, the first lowersemiconductor layer 23 a and the second lower semiconductor layer 23 bare separated from each other by the isolation groove 30 a.

Referring to FIG. 2, other electrode portions are not disposed in themesa isolation groove 27 a except for the first electrode pad 37 and thesecond electrode pad 35, and the lower semiconductor layers 23 a, 23 bmay be exposed through the mesa isolation groove 27 a.

The first light emitting cell C1 may have the same shape as the secondlight emitting cell C2 and the third light emitting cell D1 may have thesame shape as the fourth light emitting cell D2. Here, due to thestructure of the second electrode pad 35, the third light emitting cellD1 and the fourth light emitting cell D2 may have a slightly differentshape than the first light emitting cell C1 and the second lightemitting cell C2. These light emitting cells C1, C2, D1, D2 maygenerally have an elongated rectangular shape.

The first electrode pad 37 is disposed near one edge 21 a of thesubstrate 21 and the second electrode pad 35 is disposed near the otheredge 21 b of the substrate 21 facing the one edge 21 a. As shown in FIG.1, the first electrode pad 37 and the second electrode pad 35 may bedisposed to face each other. The first electrode pad 37 and the secondelectrode pad 35 are disposed on the mesa isolation groove 27 a. Inaddition, the first electrode pad 37 may be formed to straddle the firstlight emitting cell C1 and the second light emitting cell C2. The firstelectrode pad 37 and the second electrode pad 35 will be described indetail below with reference to FIG. 5 and FIG. 7.

The transparent electrode layer 33 is disposed on each of the lightemitting cells. The transparent electrode layer 33 is connected to theupper semiconductor layer 27. The transparent electrode layer 33 may beformed of a light transmissive and electrically conductive material, forexample, a conductive oxide such as ITO, ZnO and IZO or a lighttransmissive metal such as Ni/Au. The transparent electrode layer 33 haslower sheet resistance than the upper semiconductor layer 27 and thusserves to distribute electric current over a wide area. In addition, thetransparent electrode layer 33 forms ohmic contact with the uppersemiconductor layer 27 to input electric current to the uppersemiconductor layer 27.

The lower semiconductor layer 23 a or 23 b is exposed through the uppersemiconductor layer 27 and the active layer 25 of each of the lightemitting cells, and the lower extension portion 35 a or 35 b is disposedin an exposed region of the lower semiconductor layer 23 a or 23 b. Thelower extension portions 35 a, 35 b are electrically connected to thelower semiconductor layers 23 a, 23 b.

The lower extension portions 35 a disposed on the first light emittingcell C1 and the second light emitting cell C2 may include linearregions, respectively, and the linear regions may be parallel to eachother. In addition, as shown in FIG. 1 and FIG. 4, the lower extensionportion 35 a of the first light emitting cell C1 may be coaxial with alinear region of the lower extension portion 35 b of the third lightemitting cell D1.

Each of the lower extension portions 35 b disposed on the third lightemitting cell D1 and the fourth light emitting cell D2 may be connectedto the second electrode pad 35 and may include the linear region and acurved region. The curved region of the lower extension portion mayconnect the linear region thereof to the second electrode pad 35. Thelower extension portions 35 b in the linear regions on the third lightemitting cell D1 and the fourth light emitting cell D2 may be parallelto each other. Further, the lower extension portion 35 b may extendalong the center of each of the light emitting cells D1, D2.

The upper extension portions 37 a, 37 b, 37 c, 37 d are disposed on thetransparent electrode layer 33. A secondary upper extension portion 37 aand a primary upper extension portion 37 b are disposed on each of thefirst and second light emitting cells C1, C2, and a secondary upperextension portion 37 c and a primary upper extension portion 37 d aredisposed on each of the third and fourth light emitting cells D1, D2.

The primary upper extension portion 37 b disposed on each of the firstlight emitting cell C1 and the second light emitting cell C2 surrounds adistal end of the lower extension portion 35 a and a portion of a sidesurface thereof. Herein, the inside of the lower extension portion 35 ameans a side of the lower extension portion 35 a that is closer to themesa isolation groove 27 a, and the outside of the lower extensionportion 35 a means the other side of the lower extension portion 35 a.In this structure, a portion of the primary upper extension portion 37 bis disposed outside the lower extension portion 35 a, another portionthereof is disposed inside the lower extension portion 35 a, and a thirdportion thereof is disposed between the distal end of the lowerextension portion 35 a and the one edge 21 a of the substrate 21. Inaddition, the primary upper extension portion 37 b has two ends, whichare placed inside and outside the lower extension portion 35 a,respectively. The primary upper extension portion 37 b may have asymmetrical structure with respect to a straight line extending from thelower extension portion 35 a.

The primary upper extension portion 37 b extends from the one edge 21 aside of the substrate 21, at which the first electrode pad 37 isdisposed, towards the other edge 21 b side thereof, at which the secondelectrode pad 35 is disposed. As shown in FIG. 1, the distance betweenthe primary upper extension portion 37 b and the lower extension portion35 a may be variable. For example, the distance between the primaryupper extension portion 37 b and the lower extension portion 35 a mayincrease and then decrease along an imaginary line extending from theprimary upper extension portion 37 b. The distance from the lowerextension portion 35 a to the primary upper extension portion 37 b maybe generally greater than the distance from the primary upper extensionportion 37 b to an edge of a first lower semiconductor layer 23 a or tothe mesa isolation groove 27 a. Here, the distance from an inner end (onthe inside of the lower extension portion 35 a) or outer end (theoutside of the lower extension portion 35 a) of the primary upperextension portion 37 b to the lower extension portion 35 a may beshorter than the distance from the outer end thereof to the edge of thefirst lower semiconductor layer 23 a or the distance from the inner endthereof to the mesa isolation groove 27 a. With this structure, thelight emitting diode can prevent current crowding at corners of thefirst light emitting cell C1 or the second light emitting cell C2,thereby achieving uniform current spreading.

The secondary upper extension portion 37 a disposed on each of the firstlight emitting cell C1 and the second light emitting cell C2 connectsthe first electrode pad 37 to the primary upper extension portion 37 b.The secondary upper extension portion 37 a may have a linear shape andis connected at one end thereof to the first electrode pad 37 and at theother end thereof to the primary upper extension portion 37 b. Aconnection point at one end of the secondary upper extension portion 37a is farther from the one edge 21 a of the substrate 21 than from thecenter of the first electrode pad 37. In addition, a connection point atthe other end of the secondary upper extension portion 37 a may bedisposed inside the lower extension portion 35 a and may be closer tothe one edge 21 a of the substrate than the distal end of the lowerextension portion 35 a.

The primary upper extension portion 37 d disposed on each of the thirdlight emitting cell D1 and the fourth light emitting cell D2 surrounds adistal end of the lower extension portion 35 b and a portion of a sidesurface thereof. Herein, the inside of the lower extension portion 35 bmeans a side of the lower extension portion 35 b that is closer to themesa isolation groove 27 a, and the outside of the lower extensionportion 35 b means the other side of the lower extension portion 35 b.In this structure, a portion of the primary upper extension portion 37 dis disposed outside the lower extension portion 35 b, another portionthereof is disposed inside the lower extension portion 35 b, and a thirdportion thereof is disposed between the distal end of the lowerextension portion 35 b and the isolation groove 30 a. In addition, theprimary upper extension portion 37 d has two ends, that is, an inner endand an outer end, which are placed inside and outside the lowerextension portion 35 b, respectively.

The primary upper extension portion 37 d extends from the isolationgroove 30 a to the other edge 21 b of the substrate 21, at which thesecond electrode pad 35 is disposed. As shown in FIG. 1, the distancebetween the primary upper extension portion 37 d and the lower extensionportion 35 b may be variable. For example, the distance between theprimary upper extension portion 37 d and the lower extension portion 35b may increase and then decrease along an imaginary line extending fromthe primary upper extension portion 37 d.

Although the primary upper extension portion 37 d may generally have asymmetrical structure with respect to the linear region of the lowerextension portion 35 b, the outer end of the lower extension portion 35b is disposed closer to the other edge 21 b of the substrate 21 than theinner end of the primary upper extension portion 37 d. That is, as shownin FIG. 1, a region of the primary upper extension portion 37 d disposedoutside the lower extension portion 35 b is longer than a region thereofdisposed inside the lower extension portion 35 b and may be curved alongthe curved region of the lower extension portion 35 b.

The distance between the distal end of the lower extension portion 35 aor 35 b and the primary upper extension portion 37 b or 37 d surroundingthe distal end of the lower extension portion 35 a or 35 b may bevariable. That is, the upper extension portion 37 b or 37 d surroundingthe distal end of the lower extension portion 35 a or 35 b may have asemi-circular shape having a variable radius. Referring to FIG. 1, adiagonal distance d2 between the distal end of the lower extensionportion 35 a or 35 b and the primary upper extension portion 37 b or 37d may be greater than a horizontal distance d1 there in between. Here,the horizontal distance d1 means a distance from the distal end of thelower extension portion 35 a or 35 b to the primary upper extensionportion 37 b or 37 d in a horizontal direction that is parallel to thesubstrate 21. In addition, the diagonal distance d2 means a distancefrom the distal end of the lower extension portion 35 a or 35 b to theprimary upper extension portion 37 b or 37 d in a slanted direction withrespect to the horizontal direction. With the structure wherein thediagonal distance d2 is greater than the horizontal distance d1, theprimary upper extension portions 37 b, 37 d may be disposed closer toupper corners of the light emitting cells, respectively. With thestructure wherein the primary upper extension portions 37 b, 37 d aredisposed closer to the upper corners of the light emitting cells, thelight emitting diode allows efficient current spreading to the uppercorners of the light emitting cells.

The secondary upper extension portion 37 c disposed on each of the thirdlight emitting cell D1 and the fourth light emitting cell D2 may extendfrom each of the primary upper extension portion 37 d towards each ofthe lower extension portion 35 a on the first or second light emittingcell C1 or C2. The secondary upper extension portion 37 c may have alinear shape and may be collinear with the lower extension portion 35 a.The secondary upper extension portion 37 c is connected at one endthereof to the primary upper extension portion 37 d and at the other endthereof to the connecting portion 35 c.

Referring to FIG. 1 and FIG. 4, each of the connecting portions 35 cconnects the secondary upper extension portion 37 c to the lowerextension portion 35 a. That is, the lower extension portion 35 a on thefirst light emitting cell C1 is connected to the secondary upperextension portion 37 c on the third light emitting cell D1 through theconnecting portion 35 c, and the lower extension portion 35 a on thesecond light emitting cell C2 is connected to the secondary upperextension portion 37 c on the fourth light emitting cell D2 throughanother connecting portion 35 c. Accordingly, the first light emittingcell C1 may be connected in series to the third light emitting cell D1and the second light emitting cell C2 may be connected in series to thefourth light emitting cell D2. Meanwhile, the first and third lightemitting cells C1, D1 are connected in parallel to the second and fourthlight emitting cells C2, D2. The connecting portions 35 c are separatedfrom the third and fourth light emitting cells D1, D2 by the insulatinglayer 32 a.

The first electrode pad 37, the second electrode pad 35, the upperextension portions 37 a, 37 b, 37 c, 37 d, the lower extension portions35 a, 35 b and the connecting portions 35 c may be formed together usingthe same material by the same process, and may have a multilayerstructure of, for example, Cr/Al/Cr/Ni/Au. However, it should beunderstood that other implementations are also possible and thesecomponents may be formed of different materials by different processes.

Meanwhile, the upper extension portions 37 a, 37 b, 37 c, 37 d, thelower extension portions 35 a, 35 b and the connecting portions 35 c mayhave symmetrical structures with respect to an imaginary line passingthrough the first electrode pad 37 and the second electrode pad 35. Inaddition, the light emitting diode according to this exemplaryembodiment may have a symmetrical structure with respect to theimaginary line passing through the first electrode pad 37 and the secondelectrode pad 35. With this structure, the light emitting diode canachieve uniform current spreading.

Referring again to FIG. 1 to FIG. 4, the current blocking layer 31 a maybe disposed under the first electrode pad 37 and may be referred to as athird current blocking layer 31 a. In addition, the current blockinglayer 31 d may be disposed under the upper extension portions 37 a, 37b, 37 c, 37 d and may be referred to as a fourth current blocking layer31 d. The fourth current blocking layer 31 d is disposed between thetransparent electrode layer 33 and the upper semiconductor layer 27 ofeach of the light emitting cells C1, C2, D1, D2 under each of the upperextension portions 37 a, 37 b, 37 c, 37 d. Furthermore, the fourthcurrent blocking layer 31 d may be connected to the insulating layer 32a disposed under the connecting portion 35 c.

The third and fourth current blocking layers 31 a, 31 d may be formed ofan insulating material and may be composed of a single layer or multiplelayers. For example, the third and fourth current blocking layers 31 aand 31 d may include SiO_(x) or SiN_(x), and may include a distributedBragg reflector (DBR) in which insulating material layers havingdifferent indices of refraction are stacked one above another. Thefourth current blocking layer 31 d prevents current from directlyflowing from the upper extension portions 37 a, 37 b, 37 c, 37 d to thelight emitting cells C1, C2, D1, D2, thereby allowing current spreadingover a wide area of the light emitting cells C1, C2, D1, D2. The fourthcurrent blocking layer 31 d may have a greater line width than the upperextension portions 37 a, 37 b, 37 c, 37 d. If the fourth currentblocking layer 31 d is too large, the fourth current blocking layer 31 dcan cause light loss through absorption of light emitted from the lightemitting cells, accordingly, preferably, the line width of the fourthcurrent blocking layer 31 d is less than three times the line width ofthe upper extension portions 37 a, 37 b, 37 c, 37 d.

In addition, referring to FIG. 3, the third current blocking layer 31 adisposed under the first electrode pad 37 to insulate the firstelectrode pad 37 from the first lower semiconductor layer 23 a.Furthermore, the third current blocking layer 31 a may also beinterposed between the first electrode pad 37 and each of the first andsecond light emitting cells C1, C2. In this structure, the third currentblocking layer 31 a may be interposed between the transparent electrodelayer 33 and the upper semiconductor layer 27.

FIG. 5 is an enlarged plan view of the first electrode pad 37 of FIG. 1and FIG. 6 is a cross-sectional view taken along line D-D of FIG. 5.

Referring to FIG. 5 and FIG. 6, the third current blocking layer 31 ahaving a larger area than the first electrode pad 37 is disposed underthe first electrode pad 37. The first electrode pad 37 is placed only onthe third current blocking layer 31 a. The first electrode pad 37 isdisposed on the mesa isolation groove 27 a to straddle the first lightemitting cell C1 and the second light emitting cell C2. In thisstructure, the third current blocking layer 31 a insulates the firstelectrode pad 37 and the first lower semiconductor layer 23 a from eachother on the mesa isolation groove 27 a. In addition, the third currentblocking layer 31 a is interposed between the transparent electrodelayer 33 and the upper semiconductor layer 27 on each of the first andsecond light emitting cells C1, C2. A part of the transparent electrodelayer 33 is disposed under the first electrode pad 37. Thus, the firstelectrode pad 37 is electrically connected to the upper semiconductorlayer 27 through the transparent electrode layer 33. The transparentelectrode layer 33 has an opening 33 a which exposes the third currentblocking layer 31 a. The openings 33 a formed in the transparentelectrode layer 33 on the first light emitting cell C1 and the secondlight emitting cell C2 may be symmetrical to each other with respect tothe mesa isolation groove 27 a.

The opening 33 a may have a partial doughnut shape. Specifically, theopening 33 a may include a concave sidewall, a convex sidewall, and aflat sidewall connecting the concave sidewall to the convex sidewall.With the structure wherein the opening 33 a is formed in the transparentelectrode layer 33, adhesion of the first electrode pad 37 can beimproved. Although the opening 33 a is formed in the transparentelectrode layer 33 in this exemplary embodiment, the opening 33 a may beformed in the third current blocking layer 31 a so as to expose theupper semiconductor layer 27.

FIG. 7 is an enlarged plan view of the second electrode pad 35 of FIG. 1and FIG. 8 is a cross-sectional view taken along line E-E of FIG. 7.

Referring to FIG. 7 and FIG. 8, the second electrode pad 35 is disposedin the mesa isolation groove 27 a to be electrically connected to thesecond lower semiconductor layer 23 b, as described above. The thirdlight emitting cell D1 and the fourth light emitting cell D2 aredisposed near the second electrode pad 35.

The insulating layer 32 b covers side surfaces of the third lightemitting cell D1 and the fourth light emitting cell D2. As shown in FIG.7 and FIG. 8, the insulating layer 32 b covers the side surfaces of thethird and fourth light emitting cells D1, D2 excluding a portion thereofthrough which the lower extension portion 35 b passes. The insulatinglayer 32 b can prevent a bonding material from contacting the uppersemiconductor layer 27 of the third light emitting cell D1 or the fourthlight emitting cell D2 and causing short circuit upon bonding of a wireto the second electrode pad 35.

The insulating layer 32 b may be separated from the transparentelectrode layer 33 and thus may be formed to have a relatively verysmall area. As a result, it is possible to reduce light loss caused bythe insulating layer 32 b.

The light emitting diode according to the exemplary embodiment can beoperated at a relatively high voltage using the light emitting cellsconnected to each other in series. As a result, the light emitting diodeaccording to the exemplary embodiment can reduce overall drivingcurrent. Furthermore, the light emitting diode according to theexemplary embodiment can achieve uniform current spreading using thelight emitting cells connected to each other in parallel, and the lowerextension portions and the upper extension portions. Furthermore, thelight emitting diode according to the exemplary embodiment can bepackaged by a typical packaging process, and a wavelength conversionlayer containing phosphors may be disposed on the light emitting diode.As a result it is possible to provide a light emitting device that emitswhite light.

FIG. 9 is a plan view of a light emitting diode according to anotherexemplary embodiment of the present disclosure, FIG. 10 is across-sectional view taken along line F-F of FIG. 9, FIG. 11 is across-sectional view taken along line G-G of FIG. 9, and FIG. 12 is across-sectional view taken along line H-H of FIG. 9. FIG. 13A is anenlarged plan view of one exemplary embodiment of a connecting portionof FIG. 9 and FIG. 13B is a cross-sectional view taken along line I-I ofFIG. 13A. FIG. 14A is an enlarged plan view of another exemplaryembodiment of the connecting portion of FIG. 9 and FIG. 14B is across-sectional view taken along line I′-I′ of FIG. 14A. The lightemitting diode according to this exemplary embodiment is substantiallythe same as the light emitting diode shown in FIG. 1 to FIG. 8 andfurther includes a first current blocking layer 31 c disposed under eachof the lower extension portions 35 a, 35 b and a second current blockinglayer 31 b disposed under the second electrode pad 35. Hereinafter, thefollowing description will focus on different features of the lightemitting diode according to this exemplary embodiment and detaileddescriptions of the same components will be omitted.

Referring to FIG. 9, FIG. 10 and FIG. 12, the first current blockinglayer 31 c may be disposed under each of the lower extension portions 35a, 35 b. As shown therein, the first current blocking layer 31 cdisposed under each of the lower extension portions 35 a, 35 b mayinclude a plurality of dots separated from one another instead of havinga single continuous line shape. That is, as shown in FIG. 9, the firstcurrent blocking layer 31 c may include a plurality of dots separatedfrom one another. Each of the dots is disposed between the lowerextension portion 35 a or 35 b and the lower semiconductor layer 23 a or23 b. In this exemplary embodiment, the first current blocking layer 31c, that is, each of the dots, has a greater width than the lowerextension portions 35 a, 35 b. Accordingly, the lower extension portion35 a or 35 b does not directly contact the lower semiconductor layer 23a or 23 b in regions between which the first current blocking layer 31 cis interposed, and contacts the lower semiconductor layer 23 a or 23 bin a region between the dots. In addition, the dots may be arranged atregular intervals or at different intervals.

The first current blocking layer 31 c may be disposed between the lowerextension portion 35 a or 35 b and the lower semiconductor layer 23 a or23 b to assist in horizontal current spreading by preventing electriccurrent crowding near the lower extension portions 35 a, 35 b. With thestructure wherein electric current broadly spreads in the horizontaldirection in a semiconductor stack, the light emitting diode can haveimproved luminous efficacy. Particularly, the first current blockinglayer 31 c may be formed to have a greater line width than the lowerextension portions 35 a, 35 b such that the lower extension portion 35 aor 35 b can be prevented from directly contacting the lowersemiconductor layer 23 a or 23 b in the regions between which the firstcurrent blocking layer 31 c is interposed. In this exemplary embodiment,the first current blocking layer 31 c is formed to have a greater linewidth than the lower extension portions 35 a, 35 b and includes theplurality of dots, thereby further improving current spreading, ascompared with the structure wherein the first current blocking layer 31c has a smaller line width than the lower extension portions 35 a, 35 b.

In this exemplary embodiment, the first current blocking layer 31 c isnot disposed at a distal end of each of the lower extension portions 35a, 35 b. That is, the distal end of each of the lower extension portions35 a, 35 b may be directly connected to the lower semiconductor layer 23a or 23 b. As used herein, direct connection means that each of thelower extension portions 35 a, 35 b is connected at the distal endthereof to the lower semiconductor layer 23 a or 23 b without a material(for example, current blocking layer) interposed there in between.Referring to FIG. 9, each of the upper extension portions 37 b, 37 d hasa structure surrounding the distal end of the lower extension portion 35a or 35 b. If the first current blocking layer 31 c is disposed at thedistal end of each of the lower extension portions 35 a, 35 b, the lowerextension portion 35 a or 35 b cannot be directly electrically connectedat the distal end thereof to the lower semiconductor layer 23 a or 23 b,thereby causing inefficient current spreading near the distal end ofeach of the lower extension portions 35 a, 35 b.

For the first current blocking layer 31 c, the number of dots may bedetermined in various ways depending upon relative lengths of the lowerextension portions 35 a, 35 b. For example, referring to FIG. 9, thefirst current blocking layers 31 c includes five dots separated from oneanother between the lower extension portion 35 a and the first lowersemiconductor layer 23 a. In addition, the first current blocking layer31 c includes six dots separated from one another between the lowerextension portion 35 b and the second lower semiconductor layer 23 b.This is because the lower extension portion 35 b on each of the thirdand fourth light emitting cells D1, D2 includes a curved region to beconnected to the second electrode pad 35 and thus has a greater lengththan the lower extension portion 35 b on each of the first and secondlight emitting cells C1, C2. For the first current blocking layer 31 c,the distances between the plural dots may be the same or different. Itshould be understood that the number of dots for the first currentblocking layer 31 c is given by way of exemplary illustration only inFIG. 9 and does not limit other exemplary embodiments of the presentdisclosure.

Further, the second current blocking layer 31 b may be disposed underthe second electrode pad 35. The second current blocking layer 31 b isdisposed between the second electrode pad 35 and the second lowersemiconductor layer 23 b to allow efficient horizontal spreading ofelectric current injected into the second lower semiconductor layer 23b. The second current blocking layer 31 b may have a smaller area thanthe second electrode pad 35. That is, the second current blocking layer31 b may have smaller widths in the horizontal and vertical directionsthereof than the second electrode pad 35 and thus may be restrictivelydisposed under some region of the second electrode pad 35. For example,the area of the second current blocking layer 31 b may be restricted to90% or less the area of the second electrode pad 35. If the area of thesecond current blocking layer 31 b exceeds 90% the area of the secondelectrode pad 35, there is a problem of increase in forward voltage Vf.Thus, with the structure wherein the area of the second current blockinglayer 31 b is set to be 90% or less compare to the area of the secondelectrode pad 35, the light emitting diode can achieve high luminousefficacy without increase in forward voltage. As in the third and fourthcurrent blocking layers 31 a and 31 d, the first and second currentblocking layer 31 c, 31 b may be formed of an insulating material andmay be composed of a single layer or multiple layers. For example, thesecond current blocking layer 31 b may include SiO_(x) or SiN_(x), andmay include a distributed Bragg reflector (DBR) in which insulatingmaterial layers having different indices of refraction are stacked oneabove another.

FIG. 13A is an enlarged plan view of one exemplary embodiment of aconnecting portion of FIG. 9 and FIG. 13B is a cross-sectional viewtaken along line I-I of FIG. 13A.

The connecting portion 35 c electrically connects two light emittingcells C1, D1 that are isolated from each other by the isolation groove30 a, and is connected at one end thereof to the lower extension portion35 a on the first light emitting cell C1 and at the other end thereof tothe secondary upper extension portion 37 c on the third light emittingcell D1. Referring to FIG. 13A, a width w1 of the connecting portion 35c may be greater than a width w2 of the lower extension portion 35 a. Inaddition, the first current blocking layer 31 c may not be disposedunder the connecting portion 35 c and the portion of the lower extensionportion 35 a that is connected to connecting portion 35 c on the firstlight emitting cell C1, so that the connecting portion 35 c and theportion of the lower extension portion 35 a that is connected to theconnecting portion 35 c may directly contact the lower semiconductorlayer 23 a. As such, with the structure wherein the connecting portion35 c having a relatively large width w1 and the portion of the lowerextension portion 35 a that is connected to the connecting portion 35 cdirectly contact the lower semiconductor layer 23 a, the light emittingdiode allows efficient horizontal current spreading along an outerperiphery of the first light emitting cell C1, in which the primaryupper extension portion 37 b is not formed. In addition, the connectingportion 35 c is formed to have a relatively large width w1 to reduce arisk of disconnection of the connecting portion 35 c, thereby improvingreliability of the light emitting diode.

Referring to FIG. 13A and FIG. 13B, the first current blocking layer 31c may be disposed in the form of plural dots between the lower extensionportion 35 a and the lower semiconductor layer 23 a. The first currentblocking layer 31 c may have a greater width than the lower extensionportion 35 a, whereby the lower extension portion 35 a can directlycontact the lower semiconductor layer 23 a only between the dots of thefirst current blocking layer 31 c. That is, a contact distance betweenthe lower extension portion 35 a and the lower semiconductor layer 23 amay be determined depending upon a separation distance d1 between thedots.

Between the first current blocking layer 31 c and the isolation groove30 a, that is, between the last dot of the first current blocking layer31 c and the isolation groove 30 a, a contact distance d2 may be greaterthan the separation distance d1 between the dots of the first currentblocking layer 31 c. That is, between the last dot of the first currentblocking layer 31 c and the isolation groove 30 a, a contact area inwhich the connecting portion 35 c and the lower extension portion 35 athat is connected to the connecting portion 35 c contact the lowersemiconductor layer 23 a may be larger than a contact area in which thelower extension portion 35 a contacts the lower semiconductor layer 23 abetween the respective dots, thereby reducing resistance. With thisstructure, the light emitting diode can achieve efficient currentspreading to the outer periphery of the first light emitting cell C1,C2. That is, the upper extension portion 37 b may not be formed at theouter periphery of the first and second light emitting cell C1, C2,thereby providing a relatively large distance d3 between the distal endof upper extension portion 37 b and the connecting portion 35 c. In thisstructure, electric current often fails to reach of the outer peripheryof the first light emitting cell C1, C2. Thus, the contact area, betweenthe last dot of the first current blocking layer 31 c and the isolationgroove 30 a, in which the connecting portion 35 c and the lowerextension portion 35 a that is connected to the connecting portion 35 ccontact the lower semiconductor layer 23 a can be increased byincreasing the separation distance d2 to reduce resistance, therebyallowing efficient dispersion of electric current to the outer peripheryof the first light emitting cell C1.

Referring to FIG. 13B, the insulating layer 32 a disposed under theconnecting portion 35 c may extend from a portion of the side surface ofthe lower semiconductor layer 23 a of the first light emitting cell C1to side surfaces of the lower semiconductor layer 23 b, the active layer25 and the upper semiconductor layer 27 of the third light emitting cellD1 and to an upper surface of the upper semiconductor layer 27 thereof.

FIG. 14A is an enlarged plan view of another exemplary embodiment of theconnecting portion 35 c of FIG. 9 and FIG. 14B is a cross-sectional viewtaken along line of FIG. 14A. The connecting portion 35 c shown in FIG.14A and FIG. 14B is substantially the same as the connecting portionshown in FIG. 13A and FIG. 13B except for the shapes of the insulatinglayer 32 a and the upper extension portion 37 b. As a result, a contactarea between the connecting portion 35 c and the lower semiconductorlayer 23 a can be changed. The following description will focus ondifferent features of the connecting portion according to this exemplaryembodiment and descriptions of the same components will be omitted.

Referring to FIG. 14A and FIG. 14B, the insulating layer 32 a furtherextends towards the first light emitting cell C1 to cover the sidesurface and a portion of an upper surface of the lower semiconductorlayer 23 a of the first light emitting cell C1, as compared with theexemplary embodiment of FIG. 13A and FIG. 13B. In this structure,between the first current blocking layer 31 c and the isolation groove30 a, a contact distance d4 of the lower extension portion 35 a and theconnecting portion 35 c between the last dot of the first currentblocking layer 31 c and end of the insulating layer 32 a which is on thefirst light emitting cell C1 can be reduced, as compared with theexemplary embodiment of FIG. 13. That is, as compared with the exemplaryembodiment of FIG. 13A and FIG. 13B, between the first current blockinglayer 31 c and the isolation groove 30 a, the contact area, between thelast dot of the first current blocking layer 31 c and end of theinsulating layer 32 a which is on the first light emitting cell C1, onwhich the connecting portion 35 c and the lower extension portion 35 athat is connected to the connecting portion 35 c contact the lowersemiconductor layer 23 a can be reduced, thereby increasing currentdensity. In this exemplary embodiment, the contact distance d4 may stillbe longer than the separation distance d1 between the dots of the firstcurrent blocking layer 31 c. Alternatively, the contact distance d4 maybe shorter than the separation distance d1 between the dots of the firstcurrent blocking layer 31 c.

Referring to FIG. 14A, a distance d5 from the distal end of the upperextension portion 37 b to the connecting portion 35 c can be reduced, ascompared with the exemplary embodiment of FIG. 13A. That is, the upperextension portion 37 b further extends towards the connecting portion 35c such that the distance d5 between the distal end of the upperextension portion 37 b and the connecting portion 35 c can be reduced,as compared with the exemplary embodiment of FIG. 13A. In the exemplaryembodiment of FIG. 14A and FIG. 14B, between the first current blockinglayer 31 c and the isolation groove 30 a, the distance d5 between thedistal end of the upper extension portion 37 b and the connectingportion 35 c having a relatively large width w1 is reduced correspondingto reduction in contact area in which the connecting portion 35 c andthe lower extension portion 35 a connected to the connecting portion 35c contact the lower semiconductor layer 23 a, in order to achieveefficient horizontal current spreading to the outer periphery of thefirst light emitting cell C1.

FIG. 15 to FIG. 17 are plan views of light emitting diodes according toother exemplary embodiments of the present disclosure. The lightemitting diode shown in FIG. 15 to FIG. 17 is similar to the lightemitting diode shown in FIG. 9 excluding structures of a first electrodepad 37, a second electrode pad 35, upper extension portions and lowerextension portions, and the number of light emitting cells. Thus, thefollowing description will focus on different features of this exemplaryembodiment and descriptions of the same components will be omitted.

FIG. 15 is a plan view of a light emitting diode according to a furtherexemplary embodiment of the present disclosure.

Referring to FIG. 15, the light emitting diode according to thisexemplary embodiment includes first to third light emitting cells C1,C2, C3, fourth to sixth light emitting cells D1, D2, D3, and seventh toninth light emitting cells E1, E2, E3 disposed on a substrate 21. Thelight emitting diode further includes a first electrode pad 37, a secondelectrode pad 35, upper extension portions 37 a, 37 b, 37 c, 37 d, 37 e,37 f, and lower extension portions 35 a, 35 b, 35 d, 35 e.

The first to third light emitting cells C1, C2, C3 may be isolated fromthe fourth to sixth light emitting cells D1, D2, D3 by an isolationgroove 30 a, respectively. In addition, the fourth to sixth lightemitting cells D1, D2, D3 are isolated from the seventh to ninth lightemitting cells E1, E2, E3 by an isolation groove 30 b, respectively.That is, a first lower semiconductor layer 23 a may be isolated from asecond lower semiconductor layer 23 b by the isolation groove 30 a, andthe second lower semiconductor layer 23 b may be isolated from a thirdlower semiconductor layer 23 c by the isolation groove 30 b.Accordingly, the first light emitting cell C1, the second light emittingcell C2 and the third light emitting cell C3 may share the first lowersemiconductor layer 23 a, and the fourth light emitting cell D1, thefifth light emitting cell D2 and the sixth light emitting cell D3 mayshare the second lower semiconductor layer 23 b. In addition, theseventh light emitting cell E1, the eighth light emitting cell E2 andthe ninth light emitting cell E3 may share the third lower semiconductorlayer 23 c. The isolation grooves 30 a, 30 b may be formed by anisolation process and the substrate 21 may be exposed through theisolation grooves 30 a, 30 b. The first light emitting cell C1, thefourth light emitting cell D1, and the seventh light emitting cell E1may be isolated from the second light emitting cell C2, the fifth lightemitting cell D2, and the eighth light emitting cell E2, respectively,by a mesa etching process in which a mesa isolation groove 27 a isformed to expose the lower semiconductor layers 23 a, 23 b, 23 c. Inaddition, the second light emitting cell C2, the fifth light emittingcell D2, and the eighth light emitting cell E2 may be isolated from thethird light emitting cell C3, the sixth light emitting cell D3, and theninth light emitting cell E3, respectively, by a mesa etching process inwhich a mesa isolation groove 27 b is formed to expose the lowersemiconductor layers 23 a, 23 b, 23 c. That is, the semiconductor stackincluding the lower semiconductor layers 23 a, 23 b, 23 c, an activelayer 25 and an upper semiconductor layer 27 are divided into the firstto ninth light emitting cells C1, C2, C3, D1, D2, D3, E1, E2, E3 by themesa isolation grooves 27 a, 27 b and the isolation grooves 30 a, 30 b.

The first light emitting cell C1 may be symmetrical to the third lightemitting cell C3 with respect to an imaginary line connecting the firstelectrode pad 37 to the second electrode pad 35. The fourth to sixthlight emitting cells D1, D2, D3 may have the same shape. The fourth tosixth light emitting cells D1, D2, D3 may have the same shape as thefirst light emitting cell C1 excluding a secondary upper extensionportion 37 a. In addition, the seventh light emitting cell E1 may besymmetrical to the ninth light emitting cell E3 with respect to animaginary line connecting the first electrode pad 37 to the secondelectrode pad 35.

In this exemplary embodiment, the second light emitting cell C2 on whichthe first electrode pad 37 is formed and the eighth light emitting cellE2 on which the second electrode pad 35 is formed have significantlydifferent shapes than other light emitting cells. The first electrodepad 37 may be disposed near one edge 21 a of the substrate 21 and thesecond electrode pad 35 may be disposed near the other edge 21 b of thesubstrate 21 facing the one edge 21 a thereof. As shown in FIG. 15, thefirst electrode pad 37 and the second electrode pad 35 may be disposedto face each other.

The first electrode pad 37 may be formed on the second light emittingcell C2. A third current blocking layer 31 a may be disposed under thefirst electrode pad 37. Specifically, the third current blocking layer31 a may be interposed between the transparent electrode layer 33 andthe upper semiconductor layer 27 under the first electrode pad 37. Thethird current blocking layer 31 a may have a greater width than thefirst electrode pad 37, whereby the third current blocking layer 31 acan insulate the first electrode pad 37 from the first lowersemiconductor layer 23 a. A part of the transparent electrode layer 33may be disposed under the first electrode pad 37. The transparentelectrode layer 33 may include an opening 33 a which exposes the thirdcurrent blocking layer 31 a. The opening 33 a may have a circular shape.With the structure wherein the opening 33 a is formed in the transparentelectrode layer 33, adhesion of the first electrode pad 37 can beimproved. However, it should be understood that the opening 33 a is notlimited to the circular shape and may have a variety of shapes so longas the opening can improve adhesion of the first electrode pad 37.

The second electrode pad 35 may be disposed on a mesa groove 27 c. Thatis, for formation of the second electrode pad 35, a lower end of theeighth light emitting cell E2 near the other edge 21 b of the substrate21 is partially removed by mesa etching to form the mesa groove 27 c.The second electrode pad 35 may be disposed in the mesa groove 27 c tobe electrically connected to the third lower semiconductor layer 23 c.

A second current blocking layer 31 b may be disposed under the secondelectrode pad 35. The second current blocking layer 31 b is disposedbetween the second electrode pad 35 and the third lower semiconductorlayer 23 c to allow efficient horizontal spreading of electric currentinjected into the third lower semiconductor layer 23 c. The secondcurrent blocking layer 31 b may have a smaller area than the secondelectrode pad 35. That is, the second current blocking layer 31 b mayhave smaller widths in the horizontal and vertical directions thereofthan the second electrode pad 35 and thus may be restrictively disposedunder some region of the second electrode pad 35. For example, the areaof the second current blocking layer 31 b may be restricted to 90% orless the area of the second electrode pad 35.

The insulating layer 32 b covers a side surface of the mesa groove 27 con which the second electrode pad 35 is disposed. As shown in FIG. 15,the insulating layer 32 b may also be formed at a portion through whichthe lower extension portion 35 b passes while covering the side surfaceof the mesa groove 27 c to form an entirely closed curve. The insulatinglayer 32 b may be first formed at the portion through which the lowerextension portion 35 b passes, and then the lower extension portion 35 bmay be formed thereon. Accordingly, the lower extension portion 35 b mayhave a higher height at a portion thereof, on which the insulating layer32 b is formed, than at other portions thereof. The insulating layer 32b can prevent a bonding material from contacting the upper semiconductorlayer 27 of the eighth light emitting cell E2 and causing short circuitupon bonding of a wire to the second electrode pad 35.

The lower extension portions 35 d disposed on the first, third, fourth,fifth, and sixth light emitting cells C1, C3, D1, D2, D3 may includelinear regions (in the vertical direction) and may be parallel to oneanother. Each of the lower extension portions 35 d may be connected atone end thereof to the connecting portion 35 c and may have the otherend separated from a primary upper extension portion 37 c and surroundedthereby. The lower extension portion 35 e is formed on the second lightemitting cell C2, includes a linear region, and may have a shorterlength than the lower extension portions 35 d due to the first electrodepad 37. As a result, the light emitting diode according to thisexemplary embodiment may have a smaller number of first current blockinglayers 31 c than the light emitting diode according to the aboveexemplary embodiment. The lower extension portion 35 e formed on thesecond light emitting cell C2 and the lower extension portion 35 bformed on the eighth light emitting cell E2 may be placed on animaginary line connecting the first electrode pad 37 to the secondelectrode pad 35.

The lower extension portion 35 a (on both the seventh and ninth lightemitting cells E1 and E3) is connected to the second electrode pad 35and includes two linear regions connected to each other. The two linearregions may be parallel to the horizontal and vertical directions of thesubstrate 21, respectively, and may be orthogonal to each other. Thelinear region in the horizontal direction connects the linear region inthe vertical direction to the second electrode pad 35. As shown in FIG.15, in order to form the lower extension portion 35 a (particularly, thelinear region in the horizontal direction), some regions of the seventhto ninth light emitting cells E1, E2, E3 near the other edge 21 b of thesubstrate 21 may be removed by mesa etching.

The lower extension portion 35 b may be formed on the eighth lightemitting cell E2. The lower extension portion 35 b may be connected atone end thereof to the second electrode pad 35 and may have the otherend surrounded by a primary upper extension portion 37 e. The lowerextension portion 35 b may have a shorter length than the other lowerextension portions 35 a, 35 d due to the second electrode pad 35,whereby the light emitting diode according to this exemplary embodimentmay have a smaller number of first current blocking layers 31 c than thelight emitting diode according to the above exemplary embodiment.

The lower extension portions 35 a, 35 b, 35 d, 35 e may be parallel toone another and may pass through the centers of the corresponding lightemitting cells. The first current blocking layers 31 c may be disposedunder each of the lower extension portions 35 a, 35 b, 35 d, 35 e. Theprimary upper extension portions 37 b, 37 c, 37 e, 37 f have a structuresurrounding the distal ends of the lower extension portions 35 e, 35 d,35 b, 35 a, respectively. Accordingly, for the same reason as describedin the exemplary embodiment of FIG. 1, the first current blocking layer31 c may not be disposed at the distal end of each of the lowerextension portions 35 a, 35 b, 35 d, 35 e.

Meanwhile, the upper extension portions 37 a, 37 b, 37 c, 37 d, 37 e, 37f may be disposed on the transparent electrode layer 33. The secondaryupper extension portion 37 a may electrically connect the primary upperextension portions 37 b, 37 c to each other on the first to third lightemitting cells C1, C2, C3. Specifically, the secondary upper extensionportion 37 a may electrically connect the primary upper extensionportions 37 b, 37 c of two light emitting cells adjacent to each otherat the right and left sides of the secondary upper extension portion 37a. The secondary upper extension portion 37 a may be formed to straddlethe two light emitting cells adjacent to each other in the horizontaldirection and may have a curved shape. For example, referring to FIG.15, the secondary upper extension portion 37 a may connect the primaryupper extension portion 37 c on the first light emitting cell C1 to theprimary upper extension portion 37 b on the second light emitting cellC2. As a result, the first light emitting cell C1 may be electricallyconnected in parallel to the second light emitting cell C2.

Secondary upper extension portions 37 d may connect the primary upperextension portions 37 c (on the fourth to sixth light emitting cells D1,D2, D3), 37 e, 37 f on the fourth to ninth light emitting cells D1, D2,D3, E1, E2, E3 to the lower extension portions 35 d, 35 e. The secondaryupper extension portion 37 d may have a linear shape and may be coaxialwith the lower extension portion 35 d or 35 e. Each of the secondaryupper extension portions 37 d may be connected at one end thereof to theprimary upper extension portion 37 c, 37 e or 37 f and at the other endthereof to the connecting portion 35 c.

The primary upper extension portions 37 b may extend from the firstelectrode pad 37 on the second light emitting cell C2. Specifically, theprimary upper extension portions 37 b may extend from one edge 21 a ofthe substrate towards the other edge 21 b thereof at which the secondelectrode pad 35 is disposed. Referring to FIG. 15, two primary upperextension portions 37 b may be formed symmetrical to each other withrespect to an imaginary line connecting the first electrode pad 37 tothe second electrode pad 35. The primary upper extension portions 37 bmay have a curved shape, and thus, the primary upper extension portions37 b are connected to the first electrode pad 37 so as to surround adistal end of the lower extension portion 35 e and a portion of the sidesurface thereof.

The primary upper extension portion 37 c may be disposed on each of thefirst, third, fourth, fifth and sixth light emitting cells C1, C3, D1,D2, D3 to surround a distal end of the lower extension portion 35 d anda portion of the side surface thereof. Accordingly, a portion of theprimary upper extension portion 37 c may be disposed at one side of thelower extension portion 35 d and another portion of the primary upperextension portion 37 c may be disposed at the other side thereof facingthe one side of the lower extension portion 35 d. The primary upperextension portion 37 c may have a symmetrical structure with respect toan imaginary line extending from the lower extension portion 35 d.

The primary upper extension portion 37 f may be disposed on each of theseventh light emitting cell E1 and the ninth light emitting cell E3 tosurround a distal end of the lower extension portion 35 a and a portionof the side surface thereof. As described above, the lower extensionportion 35 a has a shape in which two linear regions in the horizontaland vertical directions are coupled to each other, and each of theprimary upper extension portions 37 f may be disposed to surround adistal end of the linear region of the lower extension portion 35 a inthe vertical direction and a portion of the side surface thereof. Aportion of the primary upper extension portion 37 f may be disposedoutside the lower extension portion 35 a and another portion of theprimary upper extension portion 37 f may be disposed inside the lowerextension portion 35 a. Herein, the outside means a portion fartherapart from the second electrode pad 35 with reference to the lowerextension portion 35 a, and the inside means a portion disposed to facethe outside and placed closer to the second electrode pad 35. As shownin FIG. 15, a portion of the primary upper extension portion 37 fdisposed inside the lower extension portion 35 a may have a shorterdistance than a portion of the primary upper extension portion 37 fdisposed outside the lower extension portion 35 a. In this structure, adistal end of the primary upper extension portion 37 f disposed insidethe lower extension portion 35 a is separated a predetermined distancefrom a portion of the lower extension portion 35 a disposed therebelow,thereby preventing current crowding at the lower extension portion 35 a.

The primary upper extension portion 37 e may be disposed on the eighthlight emitting cell E2 to surround a distal end of the lower extensionportion 35 b and a portion of the side surface thereof. Although theprimary upper extension portion 37 e has a substantially similar shapeto the primary upper extension portion 37 c, the primary upper extensionportion 37 e has a shorter length due to the second electrode pad 35located at a lower end of the eighth light emitting cell E2.

In FIG. 15, the first, fourth and seventh light emitting cells C1, D1,E1 may define a first group, the second, fifth and eighth light emittingcells C2, D2, E2 may define a second group, and the third, sixth andninth light emitting cells C3, D3, E3 may define a third group. In eachof the groups, the light emitting cells may be electrically connected toone another in series through the secondary upper extension portions 37d and the connecting portions 35 c (on the fourth to ninth lightemitting cells D1, D2, D3, E1, E2, E3). In addition, the first group,the second group and the third group may be electrically connected toone another in parallel through the secondary upper extension portions37 a and the linear region of the lower extension portion 35 a in thehorizontal direction.

FIG. 16 is a plan view of a light emitting diode according to yetanother exemplary embodiment of the present disclosure.

Referring to FIG. 16, the light emitting diode according to thisexemplary embodiment includes first to eighth light emitting cells C1,C2, D1, D2, E1, E2, F1, F2 disposed on a substrate 21. The lightemitting diode further includes a first electrode pad 37, a secondelectrode pad 35, upper extension portions 37 a, 37 b, 37 c, 37 d, andlower extension portions 35 a, 35 b, 35 d.

The first and second light emitting cells C1, C2 may be isolated fromthe third and fourth light emitting cells D1, D2 by an isolation groove30 a, and the third and fourth light emitting cells D1, D2 may beisolated from the fifth and sixth light emitting cells E1, E2 by anisolation groove 30 b. In addition, the fifth and sixth light emittingcells E1, E2 may be isolated from the seventh and eighth light emittingcells F1, F2 by an isolation groove 30 c. The isolation grooves 30 a, 30b, 30 c may be formed by an isolation process and may expose thesubstrate 21 there through. Meanwhile, the first light emitting cell C1,the third light emitting cell D1, the fifth light emitting cell E1, andthe seventh light emitting cell F1 may be isolated from the second lightemitting cell C2, the fourth light emitting cell D2, the sixth lightemitting cell E2, and the eighth light emitting cell F2, respectively,by a mesa etching process in which a mesa isolation groove 27 a isformed to expose the lower semiconductor layers 23 a, 23 b, 23 c, 23 d.In this structure, the first light emitting cell C1 and the second lightemitting cell C2 may share a first lower semiconductor layer 23 a; thethird light emitting cell D1 and the fourth light emitting cell D2 mayshare a second lower semiconductor layer 23 b; and the fifth lightemitting cell E1 and the sixth light emitting cell E2 may share a thirdlower semiconductor layer 23 c; and the seventh light emitting cell F1and the eighth light emitting cell F2 may share a fourth lowersemiconductor layer 23 d. That is, the semiconductor stack including thelower semiconductor layers 23 a, 23 b, 23 c, 23 d, an active layer 25and an upper semiconductor layer 27 is divided into the first to eighthlight emitting cells C1, C2, D1, D2, E1, E2, F1, F2 by the mesaisolation groove 27 a and the isolation grooves 30 a, 30 b, 30 c.

Other electrode portions are not disposed in the mesa isolation groove27 a except for the first electrode pad 37 and the second electrode pad35, and the lower semiconductor layers 23 a, 23 b, 23 c, 23 d may beexposed through the mesa isolation groove 27 a. With reference to animaginary line connecting the mesa isolation groove 27 a or the firstelectrode pad 37 and the second electrode pad 35, the first lightemitting cell C1 and the second light emitting cell C2, the third lightemitting cell D1 and the fourth light emitting cell D2, the fifth lightemitting cell E1 and the sixth light emitting cell E2, and the seventhlight emitting cell F1 and the eighth light emitting cell F2 may havesymmetrical structures, respectively. Thus, the following descriptionwill focus on the first, third, fifth and seventh light emitting cellsC1, D1, E1, F1 disposed at the left of the light emitting diode.

The first, third, fifth and seventh light emitting cells C1, D1, E1, F1may be electrically connected to one another in series. In addition, thesecond, fourth, sixth and eighth light emitting cells C2, D2, E2, F2 maybe electrically connected to one another in series. Furthermore, thefirst, third, fifth and seventh light emitting cells C1, D1, E1, F1 maybe electrically connected in parallel to the second, fourth, sixth andeighth light emitting cells C2, D2, E2, F2. With the structure whereinthe plural light emitting cells are connected to one another inparallel, the light emitting diode can achieve uniform current spreadingto each of the light emitting cells, thereby suppressing the droopphenomenon by reducing voltage increase during high current driving.

The first electrode pad 37 may be disposed near one edge 21 a of thesubstrate 21 and the second electrode pad 35 may be disposed near theother edge 21 b facing the one edge 21 a. As shown in FIG. 16, the firstelectrode pad 37 may be disposed to face the second electrode pad 35.Furthermore, the first electrode pad 37 may be formed to straddle thefirst light emitting cell C1 and the second light emitting cell C2.

The shape of the first electrode pad 37 of FIG. 16 is similar to that ofthe first electrode pad of FIG. 1. A third current blocking layer 31 ahaving a larger area than the first electrode pad 37 may be disposedunder the first electrode pad 37. The first electrode pad 37 may bedisposed only on the third current blocking layer 31 a. The firstelectrode pad 37 may be disposed on the mesa isolation groove 27 a tostraddle the first light emitting cell C1 and the second light emittingcell C2. Accordingly, the third current blocking layer 31 a may insulatethe first electrode pad 37 from the first lower semiconductor layer 23 aon the mesa isolation groove 27 a. Further, the third current blockinglayer 31 a may be interposed between the transparent electrode layer 33and the upper semiconductor layer 27 on the first and second lightemitting cells C1, C2. Meanwhile, a part of the transparent electrodelayer 33 is disposed under the first electrode pad 37. The transparentelectrode layer 33 may include an opening 33 a which exposes the thirdcurrent blocking layer 31 a. The openings 33 a formed in transparentelectrode layer 33 on the first light emitting cell C1 and the secondlight emitting cell C2 may be symmetrical to each other with respect tothe mesa isolation groove 27 a.

The opening 33 a may have a semi-circular shape. With the structurewherein the opening 33 a is formed in the transparent electrode layer33, adhesion of the first electrode pad 37 can be improved. It should beunderstood that the opening 33 a is not limited to the semi-circularshape and may have any shape so long as the opening can improve adhesionof the first electrode pad 37. Although the opening 33 a is formed inthe transparent electrode layer 33 in this exemplary embodiment, theopening 33 a may be through the third current blocking layer 31 a so asto expose the upper semiconductor layer 27.

The second electrode pad 35 may be disposed in the mesa isolation groove27 a near the other edge 21 b of the substrate 21 to be electricallyconnected to the fourth lower semiconductor layer 23 d. Meanwhile, theseventh light emitting cell F1 and the eighth light emitting cell F2 maybe disposed near the second electrode pad 35. The second currentblocking layer 31 b may be disposed under the second electrode pad 35.The second current blocking layer 31 b may be disposed between thesecond electrode pad 35 and the fourth lower semiconductor layer 23 d toallow efficient horizontal spreading of electric current injected intothe fourth lower semiconductor layer 23 d. The second current blockinglayer 31 b may have a smaller area than the second electrode pad 35.That is, the second current blocking layer 31 b may have smaller widthsin the horizontal and vertical directions thereof than the secondelectrode pad 35 and thus may be restrictively disposed under someregion of the second electrode pad 35. For example, the area of thesecond current blocking layer 31 b may be restricted to 90% or less thearea of the second electrode pad 35.

The insulating layer 32 b may cover side surfaces of the seventh lightemitting cell F1 and the eighth light emitting cell F2 near the secondelectrode pad 35. Referring to FIG. 16, the insulating layer 32 b mayalso be formed at a portion through which the lower extension portion 35a passes while covering the side surfaces of the seventh light emittingcell F1 and the eighth light emitting cell F2 to form an entirely closedcurve. The insulating layer 32 b may be first formed at the portionthrough which the lower extension portion 35 a passes, and then thelower extension portion 35 a may be formed thereon. Accordingly, thelower extension portion 35 a may have a higher height at a portionthereof, on which the insulating layer 32 b is formed, than at otherportions thereof. The insulating layer 32 b can prevent a bondingmaterial from contacting the upper semiconductor layer 27 of the seventhlight emitting cell F1 or the eighth light emitting cell F2 and causingshort circuit upon bonding of a wire to the second electrode pad 35. Theinsulating layer 32 b may be separated from the transparent electrodelayer 33 and thus may be formed to have a relatively very small area.With this structure, the light emitting diode can reduce light losscaused by the insulating layer 32 b.

The lower semiconductor layers 23 a, 23 b, 23 c, 23 d may be exposedthrough the upper semiconductor layer 27 and the active layer 25 of eachof the light emitting cells, and the lower extension portions 35 a, 35b, 35 d may be disposed on exposed regions of the lower semiconductorlayers 23 a, 23 b, 23 c, 23 d. The lower extension portions 35 a, 35 b,35 d may be electrically connected to the lower semiconductor layers 23a, 23 b, 23 c, 23 d.

Each of the lower extension portions 35 b, 35 d disposed on the first tosixth light emitting cells C1, C2, D1, D2, E1, E2 may include two linearregions (in the horizontal and vertical directions) and a curved regionconnecting the two linear regions to each other. The lower extensionportion 35 b formed on each of the first and fifth light emitting cellsC1, E1 may be in mirror symmetry to the lower extension portion 35 dformed on the third light emitting cell D1. Each of the lower extensionportions 35 b, 35 d is connected at one end thereof to the connectingportion 35 c to be electrically connected to a primary upper extensionportion 37 c or 37 d of two light emitting cells adjacent to each otherin the vertical direction, and has the other end surrounded by a curvedregion of the primary upper extension portion 37 b, 37 c or 37 d, whichis formed near the center thereof. For example, one end of the lowerextension portion 35 b formed on the first light emitting cell C1 may beconnected to a secondary upper extension portion 37 a of the third lightemitting cell D1 through the connecting portion 35 c. With thisstructure, the first light emitting cell C1 can be electricallyconnected in series to the third light emitting cell D1.

In addition, referring to FIG. 16, on the first light emitting cell C1,the lower extension portion 35 b may vertically extend from a left lowerend of the first light emitting cell C1 rather than from the centerthereof and then may be bent towards the right side. On the third lightemitting cell D1, the lower extension portion 35 d may vertically extendfrom a right lower end of the third light emitting cell D1 and then maybe bent towards the left side. Further, on the fifth light emitting cellE1, the lower extension portion 35 b may vertically extend from a leftlower end of the fifth light emitting cell E1 and then may be benttowards the right side. That is, unlike the exemplary light emittingdiodes of FIG. 9 and FIG. 15, the light emitting diode according to thisexemplary embodiment may include the lower extension portions 35 b, 35d, each of which extends from the left or right side of the lower end ofthe light emitting cell rather than from the center thereof.

The lower extension portion 35 a may be formed on the seventh and eighthlight emitting cell F1, F2 and may be connected to the second electrodepad 35. The lower extension portion 35 a may include a linear region anda curved region. The curved region of the lower extension portion 35 amay connect the linear region thereof to the second electrode pad 35.Unlike the exemplary light emitting diodes of FIG. 9 and FIG. 15, thelinear region of the lower extension portion 35 a may be formed in thehorizontal direction of the light emitting diode.

First current blocking layers 31 c may be disposed under each of thelower extension portions 35 a, 35 b, 35 d. The first current blockinglayers 31 c may be separated from each other. The first current blockinglayers 31 c may be disposed between each of the lower extension portions35 a, 35 b, 35 d and each of the lower semiconductor layers 23 a, 23 b,23 c, 23 d to assist in horizontal spreading of electric currentinjected into the lower semiconductor layers 23 a, 23 b, 23 c, 23 d.Here, as in the exemplary embodiments of FIG. 9 and FIG. 15, the firstcurrent blocking layers 31 c may not be disposed at the distal ends ofthe lower extension portions 35 a, 35 b, 35 d.

Meanwhile, the upper extension portions 37 a, 37 b, 37 c, 37 d may bedisposed on the transparent electrode layer 33. A primary upperextension portion 37 b may extend from the first electrode pad 37towards a left side 21 c of the substrate 21 on the first light emittingcell C1 in the horizontal direction. Referring to FIG. 16, the primaryupper extension portion 37 b may include a round shape adjoining thefirst electrode pad 37 and two curved lines extending from the roundshape in the horizontal direction. The primary upper extension portion37 b includes two distal ends and may be disposed to surround a distalend of the lower extension portion 35 b and a portion of a side surfacethereof. Thus, a region of the primary upper extension portion 37 b maybe disposed above the lower extension portion 35 b and another region ofthe primary upper extension portion 37 b may be disposed below the lowerextension portion 35 b. Herein, a region above the lower extensionportion 35 b refers to a region adjacent to one edge 21 a of thesubstrate 21 and a region below the lower extension portion 35 b refersto a region closer to the other edge 21 b facing the one edge 21 a ofthe substrate 21 with reference to the lower extension portion 35 b.Although the primary upper extension portion 37 b may have asubstantially symmetrical structure with respect to the linear region ofthe lower extension portion 35 b, an upper end of the primary upperextension portion 37 b may be closer to the left edge 21 c of thesubstrate 21 than a lower side thereof. That is, as shown in FIG. 16,the region of the primary upper extension portion 37 b disposed abovethe lower extension portion 35 b is larger than the region of theprimary upper extension portion 37 b disposed below the lower extensionportion 35 b and may be curved along the curved region of the lowerextension portion 35 b.

A secondary upper extension portion 37 a may be formed at a left upperend or a right upper end of each of the third, fifth and seventh lightemitting cells D1, E1, F1. The secondary upper extension portion 37 amay have a linear shape in the vertical direction. The secondary upperextension portion 37 a may be connected at one end thereof to theconnecting portion 35 c and at the other end thereof to the primaryupper extension portion 37 c or 37 d. For example, on the third lightemitting cell D1, the secondary upper extension portion 37 a may beformed at the left upper end of the third light emitting cell D1 and maybe connected at one end thereof to the connecting portion 35 c to beelectrically connected to the lower extension portion 35 b of the firstlight emitting cell C1. In addition, the other end of the secondaryupper extension portion 37 a may be connected to the left upper end ofthe primary upper extension portion 37 c of the third light emittingcell D1. With this structure, the first light emitting cell C1 may beelectrically connected in series to the third light emitting cell D1 andthe third light emitting cell D1 may also be electrically connected inseries to the fifth light emitting cell E1.

A primary upper extension portion 37 c is formed on each of the thirdand seventh light emitting cells D1, F1 and may extend from the leftside 21 c of the substrate 21 towards the mesa isolation groove 27 a inthe horizontal direction. The primary upper extension portion 37 c has asubstantially similar shape to the primary upper extension portion 37 bformed on the first light emitting cell C1 and may have a mirrorsymmetry structure thereto. There are differences in a contact areabetween the primary upper extension portion 37 b and the first electrodepad 37, and a contact area and contact location between the primaryupper extension portion 37 c and the secondary upper extension portion37 a. Referring to FIG. 16, it can be seen that the contact area betweenthe upper extension portion 37 b and the first electrode pad 37 islarger than the contact area between the primary upper extension portion37 c and the secondary upper extension portion 37 a. Also, the primaryupper extension portion 37 c is disposed closer to the mesa isolationgroove 27 a. A primary upper extension portion 37 d may be formed on thefifth light emitting cell E1 and may have a mirror symmetry structurewith respect to the primary upper extension portion 37 c.

The upper extension portions and the lower extension portions on thesecond, fourth, sixth and eighth light emitting cells C2, D2, E2, F2 maybe symmetrical to the upper extension portions 37 a, 37 b, 37 c, 37 dand the lower extension portions 35 a, 35 b, 35 d on the first, third,fifth and seventh light emitting cells C1, D1, E1, F1 with reference toan imaginary line connecting the mesa isolation groove 27 a or the firstelectrode pad 37 to the second electrode pad 35.

FIG. 17 is a plan view of a light emitting diode according to yetanother exemplary embodiment of the present disclosure.

Referring to FIG. 17, the light emitting diode according to thisexemplary embodiment may include first to eighth light emitting cellsC1, C2, D1, D2, E1, E2 disposed on the substrate 21. Further, the lightemitting diode may include a first electrode pad 37, a second electrodepad 35, upper extension portions 37 a, 37 b, 37 c, 37 d, 37 e, 37 f, 37g, 37 h, and lower extension portions 35 a, 35 b, 35 d, 35 e, 35 f, 35g.

The light emitting cells C1, C2, D1, D2, E1, E2 may be isolated from oneanother by isolation grooves 30 a, 30 b, 30 c. Specifically, the firstand second light emitting cells C1, C2 may be isolated from the thirdand fourth light emitting cells D1, D2 by the isolation groove 30 a, andthe third and fourth light emitting cells D1, D2 may be isolated fromthe fifth and sixth light emitting cells E1, E2 by the isolation groove30 b. In addition, the first, third and fifth light emitting cells C1,D1, E1 may be isolated from the second, fourth and sixth light emittingcells C2, D2, E2 by the isolation groove 30 c. That is, thesemiconductor stack including lower semiconductor layers 23 a, 23 b, 23c, an active layer 25 and an upper semiconductor layer 27 is dividedinto the first to sixth light emitting cells C1, C2, D1, D2, E1, E2 bythe isolation grooves 30 a, 30 b, 30 c.

The isolation grooves 30 a, 30 b may be formed by an isolation processand may expose the substrate 21 there through. Each of the lightemitting cells has a rectangular shape, the longitudinal length of whichis greater than the transverse length thereof. The first to sixth lightemitting cells C1, C2, D1, D2, E1, E2 may be electrically connected toone another in series. Referring to FIG. 17, the first electrode pad 37is formed at a right upper side on the second light emitting cell C2 andthe second electrode pad 35 is formed on a mesa groove 27 b formed at aleft lower side of the fifth light emitting cell E1. That is, on thesubstrate 21, the first electrode pad 37 and the second electrode pad 35may be formed on a diagonal line. In addition, with reference to theisolation groove 30 c, the first light emitting cell C1 may have asymmetrical structure with respect to the fourth light emitting cell D2,and the third light emitting cell D1 may have a symmetrical structurewith respect to the sixth light emitting cell E2.

Specifically, the first electrode pad 37 may be formed at the rightupper side of the second light emitting cell C2. A third currentblocking layer 31 a may be disposed under the first electrode pad 37.Specifically, the third current blocking layer 31 a may be interposedbetween the transparent electrode layer 33 and the upper semiconductorlayer 27 under the first electrode pad 37. The third current blockinglayer 31 a has a greater width than the first electrode pad 37 and thuscan insulate the first electrode pad 37 from the first lowersemiconductor layer 23 a. A part of the transparent electrode layer 33may be disposed under the first electrode pad 37. The transparentelectrode layer 33 may include an opening 33 a which exposes the thirdcurrent blocking layer 31 a. The opening 33 a may have a circular shape.With the structure wherein the opening 33 a is formed in the transparentelectrode layer 33, adhesion of the first electrode pad 37 can beimproved. It should be understood that the opening 33 a is not limitedto the circular shape and may have any shape so long as the opening canimprove adhesion of the first electrode pad 37.

The second electrode pad 35 may be disposed in the mesa groove 27 b.That is, in order to form the second electrode pad 35, some region atthe left lower side of the fifth light emitting cell E1 is removed bymesa etching to form the mesa groove 27 b. The second electrode pad 35may be disposed in the mesa groove 27 b to be electrically connected toa third lower semiconductor layer 23 c.

A second current blocking layer 31 b may be disposed under the secondelectrode pad 35. The second current blocking layer 31 b is disposedbetween the second electrode pad 35 and the third lower semiconductorlayer 23 c to assist in efficient horizontal spreading of electriccurrent injected into the third lower semiconductor layer 23 c. Thesecond current blocking layer 31 b may have a smaller area than thesecond electrode pad 35. That is, the second current blocking layer 31 bmay have smaller widths in the horizontal and vertical directionsthereof than the second electrode pad 35 and thus may be disposed insome region of the second electrode pad 35. For example, the area of thesecond current blocking layer 31 b may be restricted to 90% or less thearea of the second electrode pad 35.

The insulating layer 32 b may cover a side surface of the mesa groove 27b. As shown in FIG. 17, the insulating layer 32 b may also be formed ata portion through which the lower extension portion 35 a passes whilecovering the side surface of the mesa groove 27 b to have an entirelyclosed line shape. In addition, the insulating layer 32 b may be firstformed at the portion through which the lower extension portion 35 apasses, and then the lower extension portion 35 a may be formed thereon.Accordingly, the lower extension portion 35 a may have a higher heightat a portion thereof, on which the insulating layer 32 b is formed, thanat other portions thereof. The insulating layer 32 b can prevent abonding material from contacting the upper semiconductor layer 27 of thefifth light emitting cell E1 and causing short circuit upon bonding of awire to the second electrode pad 35.

The lower semiconductor layers 23 a, 23 b, 23 c may be exposed throughthe upper semiconductor layer 27 and the active layer 25 of each of thelight emitting cells, and the lower extension portions 35 a, 35 b, 35 d,35 e, 35 f, 35 g may be disposed on exposed regions of the lowersemiconductor layers 23 a, 23 b, 23 c. The lower extension portions 35a, 35 b, 35 d, 35 e, 35 f, 35 g may be electrically connected to thelower semiconductor layers 23 a, 23 b, 23 c.

The lower extension portion 35 g is formed on the second light emittingcell C2 and has a linear shape. The lower extension portion 35 g may beformed along a central line of the second light emitting cell C2. Thelower extension portion 35 g may be collinear with the linear region(horizontal direction) of the lower extension portion 35 f of the firstlight emitting cell C1. The lower extension portion 35 g may beconnected at one end thereof to the connecting portion 35 c to beelectrically connected to a primary upper extension portion 37 c of thefirst light emitting cell C1. With this structure, the second lightemitting cell C2 may be electrically connected in series to the firstlight emitting cell C1. The other end of the lower extension portion 35g may be surrounded by the primary upper extension portion 37 b. In thisexemplary embodiment, since the first electrode pad 37 is formed on thesecond light emitting cell C2, the lower extension portion 35 g may havea relatively short length.

The lower extension portion 35 f is formed on the first light emittingcell C1 and may include two linear regions (in the horizontal andvertical directions) and a curved region connecting the two linearregions to each other. The linear region of the lower extension portion35 f in the vertical direction is disposed at a left lower side of thefirst light emitting cell C1, and may be connected at one end thereof tothe connecting portion 35 c to be connected to a secondary upperextension portion 37 a of the third light emitting cell D1 and at theother end thereof to the curved region thereof. With this structure, thefirst light emitting cell C1 may be electrically connected in series tothe third light emitting cell D1. In order to form the linear region ofthe lower extension portion 35 f in the vertical direction, some regionat the left lower side of the first light emitting cell C1 may beremoved by mesa etching. In addition, the linear region of the lowerextension portion 35 f in the horizontal direction may be formed alongthe central line of the first light emitting cell C1, and may beconnected at one end thereof to the curved region thereof and may havethe other end surrounded by a primary upper extension portion 37 c.

The lower extension portion 35 e is formed on the third light emittingcell D1 and may include a linear shape. The lower extension portion 35 emay be formed along a central line of the third light emitting cell D1.The lower extension portion 35 e may be collinear with the linear region(horizontal direction) of the lower extension portion 35 d of the fourthlight emitting cell D2. The lower extension portion 35 e may beconnected at one end thereof to the connecting portion 35 c to beelectrically connected to the secondary upper extension portion 37 h ofthe fourth light emitting cell D2. With this structure, the third lightemitting cell D1 may be electrically connected in series to the fourthlight emitting cell D2. The other end of the lower extension portion 35e may be surrounded by the primary upper extension portion 37 d.

The lower extension portion 35 d is formed on the fourth light emittingcell D2 and may have a symmetrical structure to the lower extensionportion 35 f formed on the first light emitting cell C1 with referenceto the isolation groove 30 c.

The lower extension portion 35 a is formed on the fifth light emittingcell E1 and may include a curved region and a linear region. The curvedregion of the lower extension portion 35 a may be connected at one endthereof to the second electrode pad 35 and at the other end thereof toone end of the linear region of the lower extension portion 35 a. Theother end of the linear region of the lower extension portion 35 a maybe surrounded by a primary upper extension portion 37 g. In addition,the linear region of the lower extension portion 35 a may be formed atthe center of the fifth light emitting cell E1.

The lower extension portion 35 b is formed on the sixth light emittingcell E2 and may have a symmetrical structure to the lower extensionportion 35 e formed on the third light emitting cell D1 with referenceto the isolation groove 30 c.

First current blocking layers 31 c may be disposed under each of thelower extension portions 35 a, 35 b, 35 d, 35 e, 35 f, 35 g. The firstcurrent blocking layers 31 c may be separated from each other. The firstcurrent blocking layers 31 c may be disposed between each of the lowerextension portions 35 a, 35 b, 35 d, 35 e, 35 f, 35 g and each of thelower semiconductor layers 23 a, 23 b, 23 c to assist in horizontalspreading of electric current injected into the lower semiconductorlayers 23 a, 23 b, 23 c. Here, the first current blocking layers 31 cmay not be disposed at the distal ends of the lower extension portions35 a, 35 b, 35 d, 35 e, 35 f, 35 g.

Meanwhile, the upper extension portions 37 a, 37 b, 37 c, 37 d, 37 e, 37f, 37 g, 37 h may be disposed on the transparent electrode layer 33. Aprimary upper extension portion 37 b may extend from the first electrodepad 37 towards the isolation groove 30 c on the second light emittingcell C2. The primary upper extension portion 37 b may be disposed tosurround the distal end of the lower extension portion 35 g and aportion of a side surface thereof. Accordingly, a portion of the primaryupper extension portion 37 b may be disposed above the lower extensionportion 35 g, another portion thereof may be disposed below the lowerextension portion 35 g, and a third portion thereof may be disposedbetween the distal end of the lower extension portion 35 g and an edge21 d of the substrate 21. In addition, the primary upper extensionportion 37 b has two ends, which are disposed above and below the lowerextension portion 35 g, respectively. Herein, a region above the lowerextension portion 35 g refers to a region adjacent to one edge 21 a ofthe substrate 21 and a region below the lower extension portion 35 grefers to a region adjacent to the isolation groove 30 a. The distancebetween the primary upper extension portion 37 b and the lower extensionportion 35 g may be variable. For example, the distance between theprimary upper extension portion 37 b and the lower extension portion 35g may increase and then decrease along an imaginary line extending fromthe primary upper extension portion 37 b.

The primary upper extension portion 37 c may extend from the isolationgroove 30 c towards the left side 21 c of the substrate 21 on the firstlight emitting cell C1 in the horizontal direction. The primary upperextension portion 37 c may have a curved shape. The primary upperextension portion 37 c may be disposed to surround a distal end of thelower extension portion 35 f and a portion of a side surface thereof (inthe horizontal direction). Accordingly, a portion of the primary upperextension portion 37 c may be disposed above the lower extension portion35 f, another portion thereof may be disposed below the lower extensionportion 35 f, and a third portion thereof may be disposed between thedistal end of the lower extension portion 35 f and the isolation groove30 c. In addition, the primary upper extension portion 37 c has twoends, which may be disposed above and below the lower extension portion35 f, respectively. The primary upper extension portion 37 c may have asymmetrical structure with reference to an imaginary line extending fromthe linear region of the lower extension portion 35 f.

The primary upper extension portion 37 c is formed on the first lightemitting cell C1 and is similar to a primary upper extension portion 37f of the sixth light emitting cell E2 excluding a region thereof towhich the secondary upper extension portion 37 a is connected. Inaddition, primary upper extension portions 37 d, 37 e are formed on thethird light emitting cell D1 and the fourth light emitting cell D2,respectively, and may be substantially in mirror symmetry to the primaryupper extension portion 37 c excluding a region thereof to which thesecondary upper extension portion 37 a or 37 h is connected.

A primary upper extension portion 37 g may extend from the isolationgroove 30 c towards the left side 21 c of the substrate 21 on the fifthlight emitting cell E1 in the horizontal direction. The primary upperextension portion 37 g may be disposed to surround the distal end of thelower extension portion 35 a and a portion of a side surface thereof.Accordingly, a portion of the primary upper extension portion 37 g maybe disposed above the lower extension portion 35 a, another portionthereof may be disposed below the lower extension portion 35 a, and athird portion thereof may be disposed between the distal end of thelower extension portion 35 a and the isolation groove 30 c. The distancebetween the primary upper extension portion 37 g and the lower extensionportion 35 a may be variable. For example, the distance between theprimary upper extension portion 37 g and the lower extension portion 35a may increase and then decrease along an imaginary line extending fromthe primary upper extension portion 37 g. Although the primary upperextension portion 37 g may have a substantially symmetrical structurewith respect to the linear region of the lower extension portion 35 a,an upper end of the lower extension portion 35 a may be disposed closerto the left side 21 c of the substrate 21 than a lower end thereof. Thatis, as shown in FIG. 17, a region of the primary upper extension portion37 g disposed above the lower extension portion 35 a has a greaterlength than a region of the primary upper extension portion 37 gdisposed below the lower extension portion 35 a, and the primary upperextension portion 37 g may be curved along the curved region of thelower extension portion 35 a.

Meanwhile, the secondary upper extension portion 37 a formed on each ofthe third and sixth light emitting cells D1, E2 may connect the lowerextension portion to the primary upper extension portion between twolight emitting cells adjacent to each other in the vertical direction.For example, the secondary upper extension portion 37 a formed on thethird light emitting cell D1 may be connected at one end thereof to theconnecting portion 35 c to be electrically connected to the lowerextension portion 35 f formed on the first light emitting cell C1. Inaddition, the other end of the secondary upper extension portion 37 aformed on the third light emitting cell D1 may be connected to theprimary upper extension portion 37 d. With this structure, the firstlight emitting cell C1 may be electrically connected in series to thethird light emitting cell D1. The secondary upper extension portion 37 aextends at an angle from one side of an upper end of the light emittingcell towards a right or left lower end thereof to be connected to theprimary upper extension portion 37 d or 37 f.

Further, the secondary upper extension portion 37 h formed on each ofthe first, fourth and fifth light emitting cells C1, D2, E1 may connectthe lower extension portion to the primary upper extension portionbetween two light emitting cells adjacent to each other in thehorizontal direction. For example, the secondary upper extension portion37 h formed on the first light emitting cell C1 may be connected at oneend thereof to the connecting portion 35 c to be electrically connectedto the lower extension portion 35 g formed on the second light emittingcell C2. In addition, the other end of the secondary upper extensionportion 37 h formed on the first light emitting cell C1 may be connectedto the center of the primary upper extension portion 37 c. With thisstructure, the first light emitting cell C1 may be electricallyconnected in series to the second light emitting cell C2. The secondaryupper extension portion 37 h have a linear shape and may be disposedcollinear with the lower extension portion 35 b, 35 e or 35 g.

FIG. 18A, FIG. 18B, and FIG. 18C are sectional views of the lightemitting diodes according to the exemplary embodiments of the presentdisclosure, showing side surfaces thereof. Embodiments of a side surfaceof a substrate shown in FIG. 18A, FIG. 18B, and FIG. 18C may be appliedto side surfaces of the light emitting diodes shown in FIG. 1, FIG. 9and FIG. 15 to FIG. 17.

Specifically, on the side surface of the light emitting diode shown inFIG. 18A, a patterned substrate 21 is exposed and a semiconductor stackhas steps formed thereon. The patterned substrate 21 is exposed throughan isolation process and the steps are formed by mesa etching. That is,first, the patterned substrate 21 is exposed on the side surface of thelight emitting diode through the isolation process, and a step is thenformed on the lower semiconductor layer 23 b through mesa etching. Thesteps formed on the semiconductor stack can improve coupling force uponmetal deposition.

On the side surface of the light emitting diode shown in FIG. 18B, thepatterned the substrate 21 is exposed and the semiconductor stack doesnot have a step, unlike the light emitting diode shown in FIG. 18A. Thisstructure is obtained by performing the isolation process subsequent tomesa etching, unlike FIG. 18A.

On the side surface of the light emitting diode shown in FIG. 18C, thesubstrate 21 is not exposed and the semiconductor stack has steps formedthereon, unlike FIG. 18A and FIG. 18B. This structure is obtained bymesa etching alone without performing the isolation process with respectto the side surface of the light emitting diode. Since the semiconductorstack, that is, a luminous area, is inevitably removed during theisolation process, the side surface of the light emitting diode shown inFIG. 18C can secure as large a luminous area as possible by omitting theisolation process.

The light emitting diode according to the exemplary embodiments can beoperated at a relatively high voltage using the light emitting cellsconnected to each other in series. As a result, the light emitting diodeaccording to the exemplary embodiments can reduce overall drivingcurrent. Furthermore, the light emitting diode according to theexemplary embodiments can achieve uniform current spreading using thelight emitting cells connected to each other in parallel, and the lowerextension portions and the upper extension portions. Furthermore, thelight emitting diode according to the exemplary embodiments can bepackaged by a typical packaging process, and a wavelength conversionlayer containing phosphors may be disposed on the light emitting diode.As a result, it is possible to provide a light emitting device emittingwhite light.

FIG. 19 is a top view of light emitting diodes according to exemplaryembodiments of the present disclosure, showing a package mountingstructure. FIG. 19 shows a package of the light emitting diode shown inFIG. 9 bonded to a lead frame through wire bonding. It should beunderstood that the light emitting diodes of FIG. 1 and FIG. 15 to FIG.17 may also be packaged instead of the light emitting diode shown inFIG. 9.

Although certain exemplary embodiments have been described herein, itshould be understood by those skilled in the art that these embodimentsare given by way of illustration only, and that various modifications,variations, and alterations can be made without departing from thespirit and scope of the inventive concepts. Therefore, the scope of theinventive concepts should be limited only by the accompanying claims andequivalents thereof.

What is claimed is:
 1. A light emitting diode comprising: a substrate; asemiconductor stack, wherein the semiconductor stack is disposed on thesubstrate, and the semiconductor stack further comprises a lowersemiconductor layer, an upper semiconductor layer, an active layer, andan isolation groove, wherein the active layer is interposed between thelower semiconductor layer and the upper semiconductor layer, and theisolation groove exposes the substrate through the upper semiconductorlayer, the active layer and the lower semiconductor layer; a firstelectrode pad; an upper extension portion, wherein the upper extensionportion and the first electrode pad both electrically connected to theupper semiconductor layer; a second electrode pad; a lower extensionportion, wherein the lower extension portion and the second electrodepad both electrically connected to the lower semiconductor layer; aconnecting portion, wherein the connecting portion connects the upperextension portion and the lower extension portion to each other acrossthe isolation groove, a width of the connecting portion is greater thana width of the upper extension portion and a width the lower extensionportion; a first current blocking layer is disposed under the upperextension portion; and an first insulating layer, wherein the firstinsulating layer is interposed between the connecting portion and theisolation groove wherein a width of the first insulating layer isgreater than a width of the connecting portion; wherein the firstcurrent blocking layer connects to the first insulating layer.
 2. Thelight emitting diode of claim 1, further comprising: a second currentblocking layer, wherein the second current blocking layer is interposedbetween the lower extension portion and the lower semiconductor layer.3. The light emitting diode of claim 2, wherein the second currentblocking layer further comprises a plurality of dots separated from oneanother, a width of each of the dots is greater than a width of thelower extension portion.
 4. The light emitting diode of claim 3, ashortest distance, which is from the isolation groove to the dot that isclosest to the isolation groove, is difference comparing to a separationdistance between the two adjacent dots.
 5. The light emitting diode ofclaim 3, wherein a width of the connecting portion is greater than awidth of the lower extension portion between the dots.
 6. The lightemitting diode of claim 5, wherein the lower extension portion isconnected to the lower semiconductor layer between the two adjacentdots; and a distal end of lower extension portion is connected to thelower semiconductor layer.
 7. The light emitting diode of claim 6,wherein the distal end of lower extension portion is surrounded by theupper extension portion.
 8. The light emitting diode of claim 2, whereinthe first current blocking layer and the second current blocking layerfurther comprise an SiO₂ layer.
 9. The light emitting diode of claim 1,further comprising: a transparent electrode layer disposed on the uppersemiconductor layer, wherein a portion of the transparent electrodelayer is disposed between the upper semiconductor layer and the firstelectrode pad, and between the upper semiconductor layer and the upperextension portion.
 10. The light emitting diode of claim 9, wherein thefirst electrode pad is connected to a third current blocking layerthrough an opening in the transparent electrode layer.
 11. The lightemitting diode of claim 9, wherein the first insulating layer disposedunder the transparent electrode layer.
 12. The light emitting diode ofclaim 1, wherein the semiconductor stack further comprises a mesa grooveexposing the lower semiconductor layer; and a second insulating layercovers a side surface of the mesa groove on which the second electrodepad is disposed.
 13. The light emitting diode of claim 1, wherein thesemiconductor stack further comprises a mesa isolation groove exposingthe lower semiconductor layer, the semiconductor stack further comprisesa plurality of light emitting cells, wherein the plurality of lightemitting cells are defined by the isolation groove, and the lowerextension portion and the upper extension portion are disposed on eachof the plurality of light emitting cells.
 14. The light emitting diodeof claim 13, wherein the plurality of light emitting cells are definedby the mesa isolation groove, and the lower extension portion and theupper extension portion are disposed on each of the plurality of lightemitting cells.
 15. The light emitting diode of claim 14, wherein theconnecting portion electrically connects the upper extension portion andthe lower extension portion of two adjacent light emitting cells. 16.The light emitting diode of claim 15, wherein the plurality of lightemitting cells further comprise a first light emitting cell, a secondlight emitting cell, a third light emitting cell, and fourth lightemitting cell; the lower semiconductor layer further comprises a firstlower semiconductor layer and a second lower semiconductor layer,wherein the first lower semiconductor layer and the second lowersemiconductor layer are separated from each other by the isolationgroove; the first light emitting cell and the second light emitting cellshare the first lower semiconductor layer; the third light emitting celland the fourth light emitting cell share the second lower semiconductorlayer; the first light emitting cell is connected in series to the thirdlight emitting cell through the connecting portion; and the second lightemitting cell is connected in series to the fourth light emitting cellthrough the connecting portion.
 17. The light emitting diode of claim16, wherein the lower extension portions of each of the plurality oflight emitting cells further comprises a linear region, wherein theplurality of linear regions extends in the same direction, the linearregion of the lower extension portion of the first light emitting cellis coaxial with the linear region of the lower extension portion of thethird light emitting cell, the linear region of the lower extensionportion of the second light emitting cell is coaxial with the linearregion of the lower extension portion of the fourth light emitting cell.18. The light emitting diode of claim 6, wherein: a horizontal distancecomprises a distance from the distal end of the lower extension portionto the upper extension portion in a horizontal direction that isparallel to the substrate, a diagonal distance comprises a distance fromthe distal end of the lower extension portion to the upper extensionportion in a slanted direction with respect to the vertical direction,and the diagonal distance is greater than the horizontal distance.